No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Sulfur-containing Odorants in Fragrance Chemistry
Abstract
Sulfur-containing compounds are some of the strongest odorants. The perception of their odors often depends on their concentration as well as on their chemical, diastereo- and enantiomeric purity. Even if present only in trace amounts, they may change the overall olfactory impressions of fragrant mixtures, which makes the art of composing perfumes both difficult as well as rewarding. In the fruity area, compounds such as 8-mercapto-p-menthan-3-one (37), p-menthene-8-thiol (59), 3-mercapto-hexanol (62) and Oxane® (100) have gained unimpeachable superiority in terms of imparting natural fruitiness and freshness which transmits also into other olfactory domains. With regard to fragrance chemistry, the article gives a review of the particular odor properties, structure-odor correlations, biological significance and of the biochemical generation of sulfur-containing odorants.
... Sulfur-containing monoterpenoids, and especially thiols, being natural flavoring agents that impart the pleasant aroma to citrus fruits, wine, and black currants, are of interest in the exploration of flavors and fragrances [1][2][3][4]. Synthetic monoterpene thiols, known for their natural enantiomeric purity, have found applications in asymmetric synthesis. For example, pinane, menthane, and bornane thiols are used as chiral auxiliaries [5][6][7][8][9][10], chiral ligands for metal complex catalysis [11][12][13][14], organocatalysts [15], and chiral resolving agents [16]. ...
... Electrophilic thiylation of α-pinene 8 with H2S in the presence of AlBr3 (A) is followed by the pinene-menthane rearrangement, providing carbocation 10, which, when reacting with H2S, gives thiol 4. The softer Lewis acid EtAlCl2 (B) stereoselectively catalyzes the anti-addition of H2S via the formation of intermediate 11 and leads to trans-pinane-2-thiol 12 (Scheme 2) [4]. With a strong Lewis acid (BF3·Et2O) used as a catalyst, the Wagner-Meerwein rearrangement occurs to yield isobornanethiol 13 [4,46]. ...
... Electrophilic thiylation of α-pinene 8 with H2S in the presence of AlBr3 (A) is followed by the pinene-menthane rearrangement, providing carbocation 10, which, when reacting with H2S, gives thiol 4. The softer Lewis acid EtAlCl2 (B) stereoselectively catalyzes the anti-addition of H2S via the formation of intermediate 11 and leads to trans-pinane-2-thiol 12 (Scheme 2) [4]. With a strong Lewis acid (BF3·Et2O) used as a catalyst, the Wagner-Meerwein rearrangement occurs to yield isobornanethiol 13 [4,46]. Scheme 2. The addition of H2S to α-pinene 8. ...
Monoterpene thiols are one of the classes of natural flavors that impart the smell of citrus fruits, grape must and wine, black currants, and guava and are used as flavoring agents in the food and perfume industries. Synthetic monoterpene thiols have found an application in asymmetric synthesis as chiral auxiliaries, derivatizing agents, and ligands for metal complex catalysis and organocatalysts. Since monoterpenes and monoterpenoids are a renewable source, there are emerging trends to use monoterpene thiols as monomers for producing new types of green polymers. Monoterpene thioderivatives are also known to possess antioxidant, anticoagulant, antifungal, and antibacterial activity. The current review covers methods for the synthesis of acyclic, mono-, and bicyclic monoterpene thiols, as well as some investigations related to their usage for the preparation of the compounds with antimicrobial properties.
... The primary chemical components found in Chinese chives crude hexane extract are 3-Methylcyclopentanol and Phenol (Lawthienchai et al., 2016). Sulfurcontaining compounds are the strongest odorants, depending on their concentration, chemical purity, and compounds such as 8mercapto-p-menthan-3-one, p-menthene-8-thiol, 3-mercaptohexanol, and Oxane Ò have gained flawless supremacy in imparting natural fruitiness and freshness (Goeke, 2002). Volatile components isolated from Chinese chive by GC and GC-MS account for 88% of the total volatiles. ...
... They also tentatively identified two novel compounds. The results of (Goeke, 2002) and (Pino et al., 2001) also showed similarity to our research findings. ...
Objectives
The Chive chives cultivars Han Yu Zi Gen, Fu Jiu Bao F1, Shouguang Du Gen Hong, Xue Jiu, Jiu Xing 22, and Ma Lian Da Ye Bai Gen are recently evolved cultivars, and this would be the first study to characterize for agronomy, quality, volatile profile and E-Nose for aromatic and textural quality.
Methods
These cultivars were selected based on their suitability for aromatic and textural qualities that are desirable for food processing. The cultivars Han were analyzed for agronomy and quality indices by methods in general use in modern laboratories, while their volatile profile was studied by HS-SPME/GC-MS and E-nose analyses.
Results
The cultivars varied for agronomy and quality indices (P<0.05). The volatile profile showed that Esters, Heterocyclic polymers, Acids, Aldehydes, Hydrocarbons, Sulfides, Ketones, Ethers, Furfuryl derivatives, and Phenols were dominating compound groups. High total volatile contents (17.75 and 17.54 µg/g) were determined in Xue Jiu and Han Yu Zi Gen, respectively, more significant than Fu Jiu Bao F1, Ma Lian Da Ye Bai Gen, Jiu Xing 22, and Shouguang Du Gen Hong (12.22, 11.70, 10.19 and 9.53 µg/g), respectively. PCA showed that W5S and W2W were the farthest points of the first and second principal components, respectively, while W5S, W1S, W3C, W1C and W2W were main sensors classifying cultivars; where sensor W5S had larger contribution rate.
Conclusions
In this study, HS-SPME/GC-MS and E-nose methods accurately detected flavor differences among cultivars. These analyses further suggested that Xue Jiu and Han Yu Zi Gen possessed strong overall flavor characteristics; while Shouguang Du Gen Hong was the lightest in flavor characteristics. Hence it is for the general recommendation that Chinese chive cultivars Xue Jiu and Han Yu Zi Gen may be a choice of the food industry for appropriate utilization.
... More rarely, a few compounds found in essential oils contain one or more sulfur or nitrogen molecules. The presence of sulfur in particular confers an often strong, characteristic odour [3,97,98]. Sulfur-and nitrogen-containing compounds occur mainly as aglycones or glucosinolates, or their breakdown products, which include isothiocyanates. Aglycones are the nonsugar portion of a glycoside, a compound made up of a sugar group, termed the glycone, joined to another group. ...
... Other sulfur-containing compounds have been detected, frequently at trace levels, in many essential oils. Mint sulfide has been identified in many oils important in the per- fume industry, including peppermint, spearmint, pepper, ylang-ylang, narcissus, geranium, chamomile, davana [98] and rose oil [119], as well as cumin oil [120]. ...
... Their smells frequently rely on their concentrations and most importantly, on the purity of their chemical, diastereo and enantiomeric components. The skill of creating perfumes is challenging as well as rewarding because they can alter the overall olfactory perceptions of fragrant combinations even when present in small levels [27]. ...
Abstract—with the aid of an EDX analyzer (CALL ZE155, OXFORD Instruments EDX, USA), spectrometer and analytical software, eight selected Ethiopian fragrant plants were chosen for elemental analysis in the current study. They possess diverse aromatic qualities that are utilized to create a variety of odorants and fragrances. Major, minor and trace components are combined in different ways to create fragrances and cosmetics. Nine major elements (K, Ca, Si, Fe, Mg, Cl, Al, S and P), have been measured. It has been discovered that every plant has a different concentration of every element. The obtained data can be used to determine the dosage for traditional or herbal perfumeries as well as cosmopolitan consumption. The findings are useful for determining nutritional value and for creating scents and cosmetics with various combinations of various perfume plants.
... Nitrogen and sulfide compounds in the volatile compounds are mainly derived from amino acids. In particular, sulfide compounds are caused by the reaction between hydrogenated amino acids such as l-cysteine, l-methionine, and carboxylic compounds produced from fatty acids (Goeke, 2002). Dominant microorganisms might have a critical role in the production of free amino acids and headspace volatiles in cold-stored beef, which could affect VBN levels. ...
During refrigerated storage, aged beef is liable to undergo alterations in its physicochemical properties. This study aimed to evaluate changes in the community of microorganisms, volatile compounds, and amino acids in aged beef under cold storage conditions. In addition, volatile basic nitrogen (VBN) values were measured to determine the putrefaction degree. Raw‐, dry‐, and wet‐aged beef were stored at 4°C for 21 days. The initial pH of beef under the three conditions ranged from 5.52 to 5.60 and decreased from 5.04 to 5.33 over time. After 21 days, VBN values ranged 20.53–22.59 mg/100 g, which exceeded the standard of spoilage (20 mg/100 g) in the Korean Food Code. As time passed, numbers of psychrophilic and lactic acid bacteria increased in the raw beef. In contrast, number of mesophilic, psychrophilic, and lactic acid bacteria decreased in dry‐ and wet‐aged beef. Among the volatile substances and amino acids, 2,3‐butanedione, 2‐butanone, tyrosine, and arginine contributed the most to the high VBN levels in aged beef, where the VBN was 21 mg/100 g at 21 days, which was beyond the acceptable limit. In conclusion, clear alterations were observed in the physicochemical properties and microorganism communities in cold‐stored aged beef, providing basic information that could benefit the beef industry and boost consumer acceptance. Microbial, physicochemical changes due to refrigeration storage of aged Korean native cattle.
... The occurrence of volatile sulfur compounds (VSCs) in essential oils [105,106] and in food flavors was the subject of several recent reviews dedicated to their importance for the aroma and flavor of food, but also for their great chemical diversity [107][108][109][110]. Through this review, it is difficult to draw up an exhaustive list of volatile sulfur compounds; we give examples of few characteristic compounds. ...
The fragrance field of perfumes has attracted considerable scientific, industrial, cultural, and civilizational interest. The marine odor is characterized by the specific smell of sea breeze, seashore, algae, and oyster, among others. Marine odor is a more recent fragrance and is considered as one of the green and modern fragrances. The smells reproducing the marine environment are described due to their content of Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one), which is a synthetic compound. In addition to the synthetic group of benzodioxepanes, such as Calone 51 and its derivatives, three other groups of chemical compounds seem to represent the marine smell. The first group includes the polyunsaturated cyclic ((+)-Dictyopterene A) and acyclic (giffordene) hydrocarbons, acting as pheromones. The second group corresponds to polyunsaturated aldehydes, such as the (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, which are most likely derived from the degradation of polyunsaturated fatty acids. The third group is represented by small molecules such as sulfur compounds and halogenated phenols which are regarded as the main flavor compounds of many types of seafood. This review exposes, most notably, the knowledge state on the occurrence of marine ingredients in fragrance. We also provide a detailed discussion on several aspects of essential oils, which are the most natural ingredients from various marine sources used in fragrance and cosmetics, including synthetic and natural marine ingredients.
... Sulfur-containing molecules are widespread in organic synthesis,a st hey are often found in pharmaceuticals,a grochemicals,m aterials,a nd fragrances. [1][2][3][4][5] Thea bility of sulfur to adopt several different oxidation states has led to countless applications of sulfur chemistry in organic synthesis.Thus,the construction of adiverse array of sulfur-containing molecules is of strategic importance,a nd frequently involves the formation of S À Oa nd S À Nb onds. [6] Sulfonamides,s ulfoximines and sulfimides (Scheme 1) are highly relevant for medicinal chemistry and crop protection because they exhibit interesting bioactivities. ...
An iron catalyzed reaction for the selective transformation of thiols (‐SH) to sulfinamides (‐SONH2) by a direct transfer of ‐O and free ‐NH2 groups has been developed. The reaction operates under mild conditions using a bench stable hydroxylamine derived reagent, exhibits broad functional group tolerance, is scalable and proceeds without the use of any precious metal catalyst or additional oxidant. This novel, practical reaction leads to the formation of two distinct new bonds (S=O and S−N) in a single step to chemoselectively form valuable, unprotected sulfinamide products. Preliminary mechanistic studies implicate the role of the alcoholic solvent as an oxygen atom donor.
... The exchange of oxygen by sulfur in small molecular entities is an interesting phenomenon which often leads to strongly altered physico-chemical properties and hence biological properties. This is well-described for many odorants and flavors where this exchange dramatically alters detection thresholds and olfactory properties [20,21]. ...
We report on the structures of two conformers of 2-thiophenecarboxaldehyde as obtained using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemical calculations. The microwave spectrum was recorded using two spectrometers operating in the frequency ranges of 2.0 to 26.5 GHz and 26.5 to 40.0 GHz. The spectra of all singly-substituted heavy atom isotopologues ¹³C, ¹⁸O and ³⁴S in their natural abundances could be measured and assigned to determine the gas-phase substitution rs and semi-experimental reSE structures of the most abundant conformer. The spectrum of the ³³S isotopologue with its nuclear quadrupole coupling hyperfine structure was analysed, yielding the complete quadrupole tensor with high accuracy. The experimental results are used to map the observed rotational constants to the corresponding molecular structure obtained from quantum chemical calculations, which predicted two conformers with an energy difference of about 6 kJ mol⁻¹ at the MP2/6-311++G(d,p) level of theory. Insight into the conformational stability of aromatic heterocyclic carboxaldehydes and bond situations of the sulfur atom extracted from the hyperfine structure of the ³³S nucleus are discussed within the frame of the current literature. This work provides an important contribution to the study and characterisation of sulfur-containing volatile organic compounds.
... La présence de soufre, en particulier, confère un caractère d'odeur très forte [22,36,37] ...
Le cancer est une maladie complexe qui présente un réel problème de santé publique à travers le monde et cause statiquement sept millions de décès chaque année. Au cours des dernières décennies, la thérapie anticancéreuse a connu un réel bouleversement et un foisonnement de découvertes fondamentales. Plusieurs études accumulatives ont révélé l’activité antitumorale des substances naturelles isolées à partir de plantes. Les huiles essentielles (HE) et leurs constituants ont montré des activités anticancéreuses puissantes in vitro et in vivo. Cependant, les mécanismes d’action sont encore peu étudiés et moins connus. Par ailleurs, leur application dans l’industrie pharmaceutique nécessite une spécificité– sélectivité pharmacodynamique absolue. Dans le présent travail, nous présentons une synthèse des travaux réalisés sur les mécanismes d’actions anticancéreuses des HE et leurs composés bioactifs.
... Les composés terpéniques sont prédominants, mais les phénylpropanoïdes et les autres composés (composés nitriques et sulfuriques) se retrouvent avec des proportions faibles (FRIEDRICH, 1976 ;WEIDENHAMER et al., 1993 ;BOELENS,1996 ;GRIFFIN et al., 1999 ;GOEKE, 2002 ;REGNAULT-ROGER et al., 2002 ;HALKIER et GERSHENZON, 2006). Les huiles essentielles contiennent un grand nombre d'éléments biochimiques. ...
L’huile essentielle de la partie aérienne du Deverra reboudii Coss. & Durieu, obtenue par l’hydrodistillation avec une teneur moyenne de 0,5 % par rapport à la matière sèche, a été analysée par chromatographie en phase gazeuse couplée au spectromètre de masse (GC-MS) qui montre que cette huile est riche en hydrocarbures monoterpéniques (91,41 %), dont principalement : β-pinène (37,64 %), α-pinène (31,77 %), limonène (7,77 %), p-cymène (6,02 %) et β-myrcène (4,48 %). Les activités antimicrobiennes ont fait l’objet de tests sur cinq microorganismes différents. Elles indiquent que l’huile essentielle de Deverra reboudii était active contre Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Bacillus cereus et Candida albicans . Il s’agit du premier rapport sur l’étude de la composition chimique et de l’activité antimicrobienne de l’huile essentielle de cette espèce.
... Humans can perceive methional at concentrations of as little as 0.12 ng l À1 air (Belitz et al., 2009). Even if present only in trace amounts, sulphur compounds change the overall olfactory impressions of fragrant mixtures (Goeke, 2007). Thus, other, nonsulphur, main compounds such as exo-brevicomin and 2-heptanone are probably overlaid by the sulphur compounds and are of less importance for pollinator attraction. ...
Volatile emissions may play a key role in structuring pollination systems of plants with morphologically unspecialised flowers. Here we test for pollination by small mammals in Eucomis regia and investigate whether its floral scent differs markedly from fly‐ and wasp‐pollinated congeners and attracts mammals.
We measured floral traits of E. regia and made comparisons with insect‐pollinated congeners. We observed floral visitors and examined fur and faeces of live‐trapped mammals for pollen. We determined the contributions of different floral visitors to seed set with selective exclusion and established the breeding system with controlled pollination experiments. Using bioassays, we examined whether mammals are attracted by the floral scent and are effective agents of pollen transfer.
Eucomis regia differs from closely related insect‐pollinated species mainly in floral scent, with morphology, colour and nectar properties being similar. We found that mice and elephant‐shrews pollinate E. regia, which is self‐incompatible and reliant on vertebrates for seed production. Mammals are strongly attracted to the overall floral scent, which contains unusual sulphur compounds, including methional (which imparts the distinctive potato‐like scent and which was shown to be attractive to small mammals).
The results highlight the important role of scent chemistry in shifts between insect and mammal pollination systems.
... Volatile sulfur-containing compounds are among the strongest known odorants, with sensory detection thresholds in the parts per billion region or below. 1 The pronounced dosage dependency and inherent instability of sulfur compounds towards oxidation have limited their use in fragrance compositions, and they are of greater importance as flavouring agents. Sulfur-containing volatiles, such as thiols, sulfides, thiophenes, thiazoles, and others, are well recognized as important contributors to fresh and processed food aromas. ...
Novel α‐quaternary allylic thioether ketones were efficiently prepared from readily available α,β‐unsaturated ketones in an easily scalable two‐step procedure, with an acid‐catalysed skeletal rearrangement of 2‐(vinylthio) allylic alcohols as the key step. The sensory properties of this novel class of sulfur odorants were evaluated and all displayed green herbal and vegetal notes. An unexpected and interesting fresh patchouli note was observed for an alcohol derivative. Olfactory properties of a series of new sulphur compounds issued from an acid‐catalysed rearrangement of 2‐(vinylthio) allylic alcohols.
... Thiacyclopentadecane itself has been reported to have "a very weak musky smell" which becomes more apparent on heating (53). Other divalent sulfur-containing musks are known as well (54)(55)(56)(57). Consistent with previous reports (38,39), cyclopentadecanol 3 induced a weak response while cyclopentadecane 4 failed to activate OR5AN1 (SI Appendix, Fig. S1A and Table S2). ...
Significance
While natural musk has been used for 2,000 years in perfumery, and in traditional medicine for its cardioprotective effects, its mode of activating odorant receptors (ORs) is unknown. ORs, G protein-coupled receptors (GPCRs), which constitute 40% of all pharmacophore receptors, are also expressed in nonolfactory tissues. Understanding the activation of ORs at the molecular level is challenging due to lack of crystallographic models. By combining site-directed mutagenesis with computational studies of human musk ORs involving 35 chiral and achiral muscone analogues, we propose structural models, including binding site prediction and responsible amino acid residues identification. Our studies of musk-responsive ORs should assist the study of the pharmacological effects of musks involving non-OR GPCRs.
... La présence de soufre, en particulier, confère un caractère d'odeur très forte [22,36,37] ...
Cancer is a complex disease with real public health problem worldwide and causes statically 7 million deaths each year. In recent decades, cancer therapy has experienced a real upheaval and a profusion of fundamental discoveries. Several accumulative studies revealed the antitumor activity of natural substances isolated from plants. Essential oils and their constituents showed potent anticancer activity in vitro and in vivo. However, the mechanisms of action are poorly studied and least known. Furthermore, their application in the pharmaceutical industry requires a specificity-selectivity pharmacodynamic absolute. In this work, we present a summary of the works done on the mechanisms of anticancer action of essential oils and their bioactive compounds.
... The 2-methyl-3-furanthiol cooked meat-like aroma was among the five most powerful aroma compounds identified by GC-olfactometry in blackcurrant juice [65]. The flavor of 8-mercapto-p-menthan-3-one contributes to a powerful blackcurrant, cassis and catty-like aroma character, however it is a synthetic aroma, synthesized by reaction of hydrogen sulfide with (−)-pulegone from buchu leaf oil, and has not been identified in the natural blackcurrant fruit [59]. ...
Consumers’ food quality perception and sensorial experience are important in food consumption behavior and food choice. Red fruit juices are appreciated fruit juices for almost all consumers, due to their flavor and intense red color. Studies have also shown that their phytochemical composition, which is associated with their antioxidant activity, shows a protective effect against many chronic diseases. Nevertheless, the profile and concentration of anthocyanins are different in function of the fruit used; therefore, the color and health benefits of the juices also show differences. Some red fruit juices have lower concentrations of anthocyanins, for example strawberry, and others have higher concentrations, such as elderberry and black currant juices. High correlation was observed between antioxidant activity and red fruit juices’ total anthocyanins concentration. Therefore, this review will addresses red fruit juices phenolic composition, with a special focus on the challenges for future, and some ideas on the sensory impact.
... La présence de soufre, en particulier, confère un caractère d'odeur très forte [22,36,37] ...
Le cancer est une maladie complexe qui présente un réel problème de santé publique à travers le monde et cause statiquement sept millions de décès chaque année. Au cours des dernières décennies, la thérapie anticancéreuse a connu un réel bouleversement et un foisonnement de découvertes fondamentales. Plusieurs études accumulatives ont révélé l’activité antitumorale des substances naturelles isolées à partir de plantes. Les huiles essentielles (HE) et leurs constituants ont montré des activités anticancéreuses puissantes in vitro et in vivo. Cependant, les mécanismes d’action sont encore peu étudiés et moins connus. Par ailleurs, leur application dans l’industrie pharmaceutique nécessite une spécificité–sélectivité pharmacodynamique absolue. Dans le présent travail, nous présentons une synthèse des travaux réalisés sur les mécanismes d’actions anticancéreuses des HE et leurs composés bioactifs.
... Constant improvement of analytical techniques has allowed the diminution of detection thresholds and the identification of further compounds (2)(3)(4). Compound identification depends on three major points: sample preparation, analytical techniques, and data treatment. The present article gives an overview of the different sample preparation methods, especially headspace techniques, used in natural extracts analysis, and the GC detection techniques used for the identification of odorant compounds with focus on organonitrogen and organosulphur compounds. ...
Volatile nitrogen- and/or sulphur containing compounds are known for their low perception thresholds as well as for their various olfactive notes. They are present in numerous foods and natural products. Their presence, even at trace levels, can have an important effect on the matrix's organoleptic properties. Foodstuffs and natural matrices still constitute an important source of unidentified odorants. Gas chromatography (GC) is the reference method for the identification of volatile compounds, and the analyst has the choice between several extraction techniques. Different GC detection methods, especially specific detectors, are discussed. Studies of three examples of foodstuffs and natural extracts (exotic fruit, seafood, and cress absolute) known for their important content in nitrogen and sulphur compounds are presented.
... Humans can perceive methional at concentrations of as little as 0.12 ng l À1 air (Belitz et al., 2009). Even if present only in trace amounts, sulphur compounds change the overall olfactory impressions of fragrant mixtures (Goeke, 2007). Thus, other, nonsulphur, main compounds such as exo-brevicomin and 2-heptanone are probably overlaid by the sulphur compounds and are of less importance for pollinator attraction. ...
... 2. Features of the sensory stimulus: The chemical structure of an odorous compound strongly determines its perceived quality. There have been attempts to establish reliable structure-odor relationships (SOR) by linking perceptual properties to molecular vibration (Dyson 1938;Wright 1954;Wright and Serenius 1954;Wright and Michels 1964), molecular weight (Schiffman 1974b), functional group type and position (Uchida et al. 2000;Goeke 2002), molecule shape (Amoore 1963), electron donor (McGill and Kowalski 1977), acid-base character (Brower and Schafer 1975), chain length (Døving 1966), and other physicochemical parameters (for a review, see Rossiter 1996). However, all single measures have failed to reliably predict odor sensations or systematically explain odor perception so far. ...
Decoding the psychological dimensions of human odor perception has long been a central issue of olfactory research. Odor scientists as well as fragrance professionals have tried to establish comprehensive standards for the description, measurement, and prediction of odor quality characteristics. As odor percepts could not be linked to a few measurable physicochemical features of odorous compounds or physiological characteristics of the olfactory system, odor qualities have often been assessed by perception-based ratings. Although they have been applied for more than 5 decades, these psychological approaches have not yielded a comprehensive or generally accepted classification system yet. We assumed that design and methodology of these studies have largely prevented the development of unbiased odor arrangements. To address this issue, we reviewed 28 perception-based classification studies and found that their outcome has been largely determined by 4 influencing factors: 1) interindividual differences in perceptual and verbal abilities of subjects, 2) stimuli characteristics, 3) approaches of data collection, and 4) methods of data analysis. We discuss the effects of each factor in detail and illustrate how odor systems have reflected perceptual qualities as well as the conditions under which these have been assessed.
An efficient disubstituted functionalization of [1.1.1]propellane is developed. The protocol utilizes sulfonyl hydrazides and N-iodosuccinimide, enabling the introduction of iodine and sufonyl groups into bicyclo[1.1.1]pentane (BCP) in moderate to excellent yields. It has the advantages of simple operation, mild conditions, and broad substrate scope.
This study reports an efficient and green one‐step method for synthesizing thiophene‐substituted ketones from 2‐thiophenemethanol and ketones via dehydrogenative coupling using manganese complexes as catalysts. The manganese complex demonstrated a broad applicability under mild conditions and extended the range of usable substrates. Utilizing this strategy, we carried out an efficient and diverse reaction of ketones with 2‐thiophenemethanol, and successfully synthesized a series of thiophene‐substituted saturated ketones and α, β‐unsaturated ketones in good isolated yields.
Herein, we devised a synthetic approach for skeletally diversified furfuryl sulfides and 4‐alkylthiopyridines involving the heterocyclization of flexible α‐acyl ketene dithioacetals, enabled by cooperative Pd/Cu catalysis. The overall transformation was initiated by acyl‐directed desulfurative Sonogashira coupling, which was proposed as the key step in surmounting the competitive carbothiolation pathway. This step was followed by 1,6‐addition of either a S‐ or N‐nucleophile and intramolecular cyclization. Notably, the two different annulation reactions featured readily accessible starting materials, selective cleavage and reassembly of multiple chemical bonds, broad functional group tolerance, pharmacologically significant heterocyclic products with high regio‐ and chemoselectivities, and high atom economy.
Thioethers are highly prevalent functional groups in organic compounds of natural and synthetic origin but remain remarkably underexplored as starting materials in desulfurative transformations. As such, new synthetic methods are highly desirable to unlock the potential of the compound class. In this vein, electrochemistry is an ideal tool to enable new reactivity and selectivity under mild conditions. Herein, we demonstrate the efficient use of aryl alkyl thioethers as alkyl radical precursors in electroreductive transformations, along with mechanistic details. The transformations proceed with complete selectivity for C(sp ³ )−S bond cleavage, orthogonal to that of established transition metal‐catalyzed two‐electron routes. We showcase a hydrodesulfurization protocol with broad functional group tolerance, the first example of desulfurative C(sp ³ )−C(sp ³ ) bond formation in Giese‐type cross‐coupling and the first protocol for electrocarboxylation of synthetic relevance with thioethers as starting materials. Finally, the compound class is shown to outcompete their well‐established sulfone analogues as alkyl radical precursors, demonstrating their synthetic potential for future desulfurative transformations in a one‐electron manifold.
Thioethers are highly prevalent functional groups in organic compounds of natural and synthetic origin but remain remarkably underexplored as starting materials in desulfurative transformations. As such, new synthetic methods are highly desirable to unlock the potential of the compound class. In this vein, electrochemistry is an ideal tool to enable new reactivity and selectivity under mild conditions. Herein, we demonstrate the efficient use of aryl alkyl thioethers as alkyl radical precursors in electroreductive transformations, along with mechanistic details. The transformations proceed with complete selectivity for C(sp³)−S bond cleavage, orthogonal to that of established transition metal‐catalyzed two‐electron routes. We showcase a hydrodesulfurization protocol with broad functional group tolerance, the first example of desulfurative C(sp³)−C(sp³) bond formation in Giese‐type cross‐coupling and the first protocol for electrocarboxylation of synthetic relevance with thioethers as starting materials. Finally, the compound class is shown to outcompete their well‐established sulfone analogues as alkyl radical precursors, demonstrating their synthetic potential for future desulfurative transformations in a one‐electron manifold.
Herein, the use of aryl alkyl thioethers as precursors for C-centered alkyl radicals is demonstrated for desulfurative C-H and C-C bond formation under electroreductive conditions. The transformations occur with complete selectivity for C(sp3)-S bond cleavage, orthogonal to that of transition metal-catalyzed two-electron routes. Experimental and theoretical studies provide mechanistic insights that serve as a steppingstone for future use of thioethers as efficient radical precursors that can outcompete their established sulfone analogues.
Herein, the use of aryl alkyl thioethers as precursors for C-centered alkyl radicals is demonstrated for desulfurative C-H and C-C bond formation under electroreductive conditions. The transformations occur with complete selectivity for C(sp3)-S bond cleavage, orthogonal to that of transition metal-catalyzed two-electron routes. Experimental and theoretical studies provide mechanistic insights that serve as a steppingstone for future use of thioethers as efficient radical precursors that can outcompete their established sulfone analogues.
p>In depth headspace analysis of the slow degradation of beta‐alkylthioalkanones in ambient air led to the discovery of a novel d‐cleavage pathway, by which perceivable amounts of beta‑mercapto ketones are released. Since beta‑mercapto ketones are potent natural aroma compounds occurring in many fruits, herbs and flowers, the discovery of a molecular enzyme‐independent precursor for this class of high‐impact molecules is of practical importance. Moreover, the formation of beta‑diketones and aldehydes by concomitant oxidation at the alpha‐(S)‐position enhances the versatility of this class of aroma precursors. A mechanistic model is proposed which suggests that the oxidative degradation occurs via a novel Pummerer‐type rearrangement of initially formed persulfoxides. </p
A nickel-catalyzed C–SPy bond activation reactions to produce a variety of thioethers has been developed. The reaction is promoted by a user-friendly, inexpensive, air and moisture-stable Ni precatalyst. Various aryl 2-pyridyl thioethers and a wide range of alkyl and aryl thiols substrates were tolerated in this process which afforded products in moderate to excellent yields.
Allgemein verfügbare Thiole werden chemoselektiv unter Verwendung eines kostengünstigen Eisenkatalysators durch die Bildung von zwei verschiedenen neuen Bindungen (S=O und S−N) in einem einzigen Schritt zu wertvollen ungeschützten Sulfinamiden umgewandelt. Ein von Hydroxylamin abgeleitetes Reagenz fungiert als duales Oxidationsmittel und Aminogruppendonor für die Synthese von strukturell und funktionell komplexen Sulfinamiden.
Abstract
Es wurde eine eisenkatalysierte Reaktion für die selektive Umwandlung von Thiolen (‐SH) in Sulfinamide (‐SONH2) durch direkte Übertragung von ‐O und freien ‐NH2‐Gruppen entwickelt. Die Reaktion läuft unter milden Bedingungen unter Verwendung eines luftstabilen, von Hydroxylamin abgeleiteten Reagenz ab, weist eine breite Toleranz gegenüber funktionellen Gruppen auf, ist skalierbar und verläuft ohne die Verwendung eines Edelmetallkatalysators oder eines zusätzlichen Oxidationsmittels. Diese neuartige, praktische Reaktion führt zur Bildung von zwei verschiedenen neuen Bindungen (S=O und S−N) in einem einzigen Schritt, um chemoselektiv wertvolle, ungeschützte Sulfinamidprodukte zu bilden. Vorläufige mechanistische Studien implizieren die Rolle des alkoholischen Lösungsmittels als Sauerstoffatomdonor.
This paper reports on the analysis of Indian cress absolute (Tropaeolum majus L.). Indian cress is an edible cress species that belongs to the Brassicale order. Its absolute, obtained by extraction of the plant with a non-polar solvent (concrete) followed by treatment with ethanol, has never been studied. It was analyzed by GC-MS and GC-O in order to characterize its main volatile compounds and key odorants. This research made it possible to identify two new volatile compounds: N-benzyl O-ethyl thiocarbamate and O,S-diethyl thiocarbonate. To the best of our knowledge, both compounds were reported in cress extract for the first time. These molecules being of organoleptic interest, 27 homologues were further synthesized and evaluated. Among those new volatiles, N-phenyl thiocarbamates were shown to be particularly interesting for their savory and meaty odors.
A nickel‐catalyzed aryl thioether metathesis has been developed to access high‐value thioethers. 1,2‐Bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional‐group‐tolerant reaction. Furthermore, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring‐closing metathesis that does not involve alkene bonds. In‐depth organometallic studies support a reversible Ni⁰/NiII pathway to product formation. Overall, this work not only provides a more sustainable alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information that are highly relevant to the further development and application of unusual single‐bond metathesis reactions.
Nickel macht's: Eine Nickel‐katalysierte Arylthioether‐Metathese wurde für die Synthese von hochwertigen Thioethern entwickelt. Weiterhin konnten synthetisch anspruchsvolle Makrocyclen in guter Ausbeute in einem seltenen Beispiel für eine Ringschlussmetathese ohne Doppelbindungen erhalten werden. Umfassende metallorganische Untersuchungen belegen einen reversiblen Ni⁰‐NiII‐Pfad zur Produktbildung.
Abstract
Für die Synthese von hochwertigen Thioethern wurde eine Nickel‐katalysierte Arylthioether‐Metathese entwickelt. 1,2‐Bis(dicyclohexylphosphino)ethan (dcype) ist essentiell, um diese Reaktion mit breiter Kompatibilität funktioneller Gruppen zu ermöglichen. Weiterhin konnten synthetisch anspruchsvolle Makrocyclen in guter Ausbeute in einem seltenen Beispiel für eine Ringschlussmetathese ohne Doppelbindungen erhalten werden. Umfassende metallorganische Untersuchungen belegen einen reversiblen Ni⁰‐NiII‐Pfad zur Produktbildung. Insgesamt wird in dieser Arbeit nicht nur eine nachhaltigere Alternative zu früheren katalytischen Systemen auf Pd‐Basis beschrieben, sondern es werden auch neue Anwendungen und mechanistische Informationen aufgezeigt, die für die weitere Entwicklung und Anwendung ungewöhnlicher Metathesereaktionen von Einfachbindungen von hoher Relevanz sind.
Using Highly correlated ab initio methods at the CCSD(T) level, with and without the inclusion of scalar relativistic effects, accurate 3D potential energy surfaces (PESs) of CuSH and CuOH were generated in their electronic ground state. The PESs are incorporated into perturbative and variational treatments of nuclear motions. Using these approaches, we derived a set of accurate spectroscopic parameters and the pattern of the vibrational states of CuXH (X=O,S) up to 4000 cm⁻¹. The applied calculations at the CCSD(T)/aug-cc-pV5Z-DK level of theory are validated using several experimental high-resolution spectroscopy data (including rotational spectroscopy) available in the literature. The optimized equilibrium geometries of CuSH and CuOH with bending angles of 93.9° and 110.2°, Cu-X bond lengths of 2.088 Å and 1.764 Å, and X-H bond lengths of 1.344 Å and 0.961 Å, respectively, accurately reproduce the experimental structures and clearly show the importance of the scalar relativistic effects. The anharmonic frequencies, ν1, ν2, and ν3, are computed at 3655.5 cm⁻¹, 746.3 cm⁻¹, and 623.3 cm⁻¹ for CuOH and at 2572.9 cm⁻¹, 588.9 cm⁻¹, and 396.6 cm⁻¹ for CuSH, respectively. Finally, the PESs are derived as anharmonic force fields for CuXH (X=O,S) that can be incorporated into large scale molecular dynamics simulations of Cu-X containing compounds. The results are discussed within the scope of available literature on the effects of substitution of oxygen by sulfur for putative molecular recognition mechanisms.
A highly efficient and enantioselective Brønsted acid catalyzed conversion of epoxides to thiiranes has been developed. The reaction proceeds in a kinetic resolution, furnishing both epoxide and thiirane in high yields and enantiomeric purity. Heterodimer formation between the catalyst and sulfur donor affords an effective way to prevent catalyst decomposition and enables catalyst loadings as low as 0.01 mol %.
Volatile sulfur compounds are important contributors to the characteristic flavors and off-flavors of many foods. As a class, sulfur-containing flavor volatiles have low sensory detection thresholds, are present in low concentration and are often chemically labile, which can present measurement challenges. Advances in analytical separation techniques and instrumentation have enabled understandings of their occurrence and contributions to their relative sensory significance.
Essential oil, also defined as essence, volatile oil, etheric oil or aetheroleum, is a complex mixture of volatile constituents biosynthesised by living organisms. Essential oils can be liberated from their matrix by water, steam and dry distillation, or expression in the case of citrus fruits [1-5]. Their occurrence and function in nature is still a question and the subject of ongoing research. However, there is evidence that organisms produce essential oils for defence, signalling or as part of their secondary metabolism.As a consequence essential oils comprise an important bioresource for renewable natural products [1-25].
Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroarom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides a facile access to enantioenriched tertiary thioether/alcohols. The mechanism of γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “C=O” unit of donor molecules were shown to be crucial in asymmetric induction.
The enantioselective synthesis of four stereoisomers of 2-methyl-tetrahydrofuran-3-thiol acetate was achieved. The two enantiomers of the important intermediate cis-2-methyl-3-hydroxy-tetrahydrofuran were obtained by Sharpless asymmetric dihydroxylation (AD), whereas the two enantiomers of trans-2-methyl-3-hydroxy-tetrahydrofuran were derived from the corresponding optically active cis-isomers by Mitsunobu reaction. Each stereoisomer of 2-methyl-3-hydroxy-tetrahydrofuran went through mesylation and nucleophilic substitution to afford the corresponding product with specific configuration. (2R,3S)- and (2R,3R)-2-methyl-tetrahydrofuran-3-thiol acetate were obtained in 80% ee, whereas the (2S,3R)- and (2S,3S)-isomers were in 62% ee. The odor properties of the synthesized four stereoisomers were evaluated by gas chromatography-olfactometry (GC-O), which revealed perceptible differences among stereoisomers both in odor features and in intensities.
Sulfur-containing odorants and flavors play an important role in flavor and food industry, especially when meaty, garlic, onion, and vegetable scents are needed. Still, many S-containing flavors also possess fruity scents and may be used in compositions of perfumes that require a fresh and fruity odor perception. They are naturally abundant in various fruits, essential oils, and food. Most of these compounds possess strong scents, and their scent composition is highly dependent on the concentration applied. At higher concentrations, they usually feature repellent off-odors, while their sweet and fruity nature is only experienced at very low concentrations. This represents a challenge for their application in perfumery, as well as in food industry. From a molecular point of view, the endless structural and scent variety of these compounds makes them fascinating, especially as their O-analogs are usually free of any malodors. Here, we report on the investigation of the gas-phase structure and dynamics of the S-containing blackcurrant odorant cat ketone (4-methyl-4-sulfanylpentan-2-one). The work was performed by combining quantum-chemical calculations and molecular-beam Fourier-transform microwave spectroscopy as complementary tools. Using this technique, we are able to determine the structures of sizeable molecules where energy differences are small and conformational distinction is not always possible by quantum-chemical calculations alone. The presented results can be used for further structureactivity correlation studies, as well as for benchmarks to improve theoretical models, especially, as there is still significant interest in characterizing the various conformers of organic molecules in terms of relative energies, structures, and dipole moments.
Modern lifestyles create plentiful opportunities for malodour generation and proliferation. A domestic dwelling provides a number of micro-environments in which a range of malodour-producing activities such as laundry, food preparation and necessary bodily functions take place. With a significant proportion of time spent indoors, there is increasing exposure to these micro-environments. Knowledge of the chemical composition and, in particular, the key malodour components present in these situations, is crucial to understand how to limit their impact. This is a multi-disciplinary undertaking, encompassing analytical measurements, physical–organic chemistry, biology and sensory evaluation. As a consequence information can be dispersed over a number of sources in the literature and is not always readily recognizable as malodour related. The current review addresses this situation, examining the state of knowledge of household malodour composition, covering in detail areas such as food preparation and disposal, indoor air concentrations and building emissions, and body effluents. Examples to illustrate these areas are presented and discussed. Copyright © 2013 John Wiley & Sons, Ltd.
This tutorial is an introduction for PhD students and researchers who intend to start their future work in the field of microwave spectroscopy to investigate structural and dynamical aspects of isolated molecular systems in the gas phase. Although the presented case studies are related to odorants, i.e., volatile molecules that possess a noticeable scent, the background and applications of the method can be transferred to any other resembling molecular system. In the early days, microwave spectroscopy was mainly related to the structure determination of very small systems such as OCS or ammonia, where the bond lengths could be determined with high accuracy by measuring the different isotopic species of the molecules. Nowadays, the method is far more advanced and is also used to tackle various fundamental molecular problems in different fields such as physical chemistry and molecular physics. Interesting questions that can be investigated concern, e.g., the molecular structure, i.e., the different conformations, not only of the isolated molecule but also of van der Waals complexes with water, noble gases or other molecules. The dynamical and intra- or intermolecular effects can be straightforwardly observed without the influence of the environment as in the condensed phase. This evolution was only achieved by using quantum chemical methods as a complementary tool to elude the necessity of isotopologues for structure determination, which cannot be realized for large systems (>5 atoms). The combination of microwave spectroscopy and quantum chemical calculations is the method of choice when it comes to sampling the conformational space of molecules. This is particularly the case when small energy differences make it difficult to determine the conformers of the lowest energy using computational methods alone. Although quantum chemical calculations are important for the validation of microwave spectra, the focus of the tutorial is set on the experimental part of the method, as the quantum chemical part of the work is restrained on geometry optimizations using common methods, mainly Møller–Plesset second order perturbation theory and density functional theory. The aim of this tutorial is therefore to give the reader an overview on the theoretical background and the experimental setup of microwave spectroscopy, as well as a realistic estimation on the effort required to conduct similar projects.
This book takes an interdisciplinary look at the development of essential oils from the agricultural to consumer products sectors. The book espouses a product/market driven and entrepreneurial approach rather than a commodity approach, offering many new ideas and tools to assist the reader in the area of essential oil development. This book uniquely covers both the technical and business aspects in a detail that will inform readers of the complexities of essential oil development, production and business development. This book is the result of the author's thirty years experience in the industry.
The synthesis of tertiary thiols in enantiomerically enriched form is accomplished by lithiation of enantiomerically enriched N-aryl allylic thiocarbamates. Formation of an allyllithium derivative promotes intramolecular N to C aryl migration to the position α to sulfur, generally with good stereospecificity. The substrates may themselves be obtained by Pd-catalyzed enantioselective [3,3]-sigmatropic rearrangement of N-aryl O-allyl thiocarbamates. Solvolysis of the product thiocarbamates yields tertiary thiols, which may be converted to sulfide derivatives.
The use of metallic triflates and triflimidates as efficient catalysts in recent cycloisomerizations, hydroalkoxylations, hydrocarboxylations, hydrothiolations, Friedel-Crafts reactions, α-amidoalkylation and other C-C, C-O and C-S coupling reactions is reviewed.
1 Introduction
2 Preparation of Metallic Triflates and Triflimidates
2.1 Preparation from Oxides, Halides, Carbonates, and Relatives
2.2 Electrochemical Method
2.3 Oxidative Dissolution of Metallic Powders in the Presence of Superacids
3 Formation of C-C Bonds
3.1 Diels-Alder-Type Reactions
3.2 [3+2] And [2+2] Cycloadditions
3.3 Diene and Polyprenoid Cycloisomerizations
3.4 Friedel-Crafts Reactions
3.4.1 Acylation of Arenes
3.4.2 Alkylation/Benzylation of Arenes
3.4.3 Friedel-Crafts Allylation
3.4.4 Tandem Allylation-Cyclization Processes
3.5 Addition of Nucleophiles to α-Hydroxylactams via N-Acyliminium Ion Intermediates
4 Formation of C-O Bonds
4.1 Intramolecular Hydroalkoxylation of Olefins
4.2 Intermolecular Hydroalkoxylation of Olefins
4.3 Intramolecular Hydrocarboxylation of Olefins
4.4 Dealkylative Cyclization of Epoxy Esters
4.5 Intramolecular Cyclization of Unsaturated Oximes
5 Formation of C-S Bonds
5.1 Intra- and Intermolecular Electrophilic Addition of RSH and RCOSH to Olefins
5.2 Isomerization of Thionolactones to Thiolactones
6 Outlook and Future Prospects
Indium(III) chloride and indium(III) trifluoromethanesulfonate were found to be excellent catalysts for the addition of thiolacetic acid to non-activated olefins. The reaction is highly regioselective and can be run in the presence of 1mol% of catalyst.
A one-step synthesis of 6-thiabicyclo[3.2.1]octan-3-one from carvone is reported. Chiral sulfides were subsequently elaborated in a few steps and used as competent sulfonium ylide promoters for the asymmetric epoxidation of aldehydes. Their odourant characteristics are also described.
A series of thiolanes were prepd. by cyclodehydration of sulfanylalcs. in the presence of catalytic amts. of p-toluenesulfonic acid or by using K10 clay. The sulfur heterocycles were synthesized in good to excellent yields using either a conventional Dean-Stark method or microwave irradn. under solvent-free conditions. The reaction could be performed regio- and stereoselectively and its mechanism was investigated by means of enantio- and diastereomerically enriched substrates. In contrast to previous studies, our results are consistent with an intramol. SN2-type mechanism as a general pathway. [on SciFinder(R)]
Consumers demand new and improved flavor sensations, which cannot always be fulfilled by traditional flavors from known fruits. Inspiration for new developments in flavors may be generated from plant material originating from the tropical rainforests. The tropics house 80 to 90% of
all plant species and the aromatic aspects of most of these are entirely unknown. Field methods for the collection of samples, the isolation and conservation of the aroma compounds in very remote areas are presented. The overall flavor profile and the key aroma compounds of selected fruits
and 'garlic' barks collected from the Gabonese tropical rainforest 'foret des Abeilles' are described.
The use of internal standards is a classical analytical technique employed to improve quantitative accuracy. In this study, internal standards were added to grapefruit juice solvent extracts to improve the qualitative identification of aroma active compounds. In GC-Olfactometry the human response is ultimately compared to an instrumental response such as that from a mass spectrometer or flame ionization detector (FID) to identify the component responsible for the aroma activity. Using two internal standards which have both olfactometry and instrumental responses, it is possible to exactly align both aromagrams and chromatogram to reduce the uncertainty in assigning the instrumental response associated with aroma activity. The purpose for this study was to develop a set of aroma active components for citrus juices that would have unique sensory qualities, compatible retention times and produce measurable sensory and instrumental responses that could be used to synchronize both instrumental responses and aroma activity. Identification accuracy was improved when both early and late eluting aroma standards were employed. Benzaldehyde, methyl jasmonate and S-methylthio butanoate are compounds that can perform satisfactorily with citrus juice aroma extracts as aroma active internal standards.
A comparison is made of the volatile component concentrations in the macerated (blended) forms of tomato fruit and leaf and to a lesser extent in macerated flower, calyx and stem. These studies show that some processes such as the formation of C6 lipid derived volatiles are similar between fruit and leaf. Formation of higher carbon number lipid derived volatiles (e.g. 4,5-epoxy-(E)-2-decenal), however, only occurs in the fruit. Other processes such as the formation of carotenoid related (e.g. 6-methyl-5-hepten-2-one) and amino acid related (e.g. nitro, nitrile and thiazole) volatiles seem to be largely confined to the fruit. Terpenoid hydrocarbons occur in the leaf but not the fruit, except for (-)-alpha-copaene in the mature green fruit. Lipid oxidation processes occur in the first few minutes after maceration but glycoside hydrolysis and amino acid derived volatile biogenesis seems to occur during the ripening process in the intact tomato.
Das Titelbild zeigt auf der Lippe von Oncidium tigrinum La Llave et Lex. die Überlagerung von β-Jonon mit einem maßgeschneiderten Bicyclo[6.4.0]dodecen. Die gute strukurelle Übereinstimmung erklärt die geruchliche Ähnlichkeit beider Verbindungen. Im Duft der abgebildeten tropischen Orchidee findet sich der ungewöhnlich hohe Anteil von 14.5 % β-Jonon. Im Hintergrund ist ein Überblick über das olfaktorische Spektrum zu sehen. Mehr über Düfte und die ihnen zugrunde liegenden Verbindungen finden Sie im Aufsatz von P. Kraft et al. auf S. 3106 ff.
(─)-Mintsulfide [(─)-1], a new sulfur-containing sesquiterpene found in peppermint oil, was synthesized from (─)-germacrene-d[(─)-3] by a photochemical reaction and was confirmed to be (1R)-cis-2,6-epithio-cis-8-isopropyl-l-methyl-5-methylene-cis-bicyclo-[5,3,0]decane. The existence of 1 was confirmed in 13 of 74 essential oils analyzed.
Pyrolytic conversion of S-(2-alkenyl) S-alkyl dithiocarbonates (allylic dithiolcarbonates) to 2-alkenyl alkyl sulfides (allylic sulfides) was catalyzed by phenols bearing electron-attracting substituents. The reaction is pseudo-first-order and the apparent first-order rate constants are proportional not only to the concentration of phenols but also to the hydrogen-bonding capability of phenols. The entropy of activation for the phenol-catalyzed reaction is ca. 8 e.u. smaller than that for the uncatalyzed reaction. The reactivity of S-(1-phenylallyl) S-alkyl dithiocarbonates did not obey Hammett's or Taft's equation. Based on these findings together with the MNDO (modified neglect of diatomic overlap) calculation data, a possible role of phenols in the pyrolytic conversion of allylic dithiolcarbonates to allylic sulfides is discussed.
Durch Umsetzung von Enantiomerengemischen von Thiolen mit 2-Phenyl-propionylchlorid werden diastereomere Hydratropasäure-(HTS)-ester wie (I) bzw. (III) erhalten.
3-Methylthio-hexane-1-ol and 2-methyl-4-propyl-1,3-oxathiane, chiral S-containing aroma substances of the yellow passion fruit are resolved to enantiomers and absolute configurations are elucidated.
Epithiospecifier protein (ESP) activity was determined in the seeds of two cultivars of Brassica napus, in B. campestris and in Lepidium sativum. All four types of seeds contained susceptible substrates for ESP (that is, glucosinolates with terminal unsaturation in their side-chain), although L. sativum contained only a very small amount of one. Results suggest that Fe2+ is essential for ESP activity, but its presence certainly promoted the effects of ESP to a considerable extent, and even at a very low level (e.g. 6 × 10−11 mol Fe2+. Further evidence was gained for the intramolecular nature of the reaction which results in cyanoepithioalkane formation.
Computer assisted statistical methods have been used to study the odor thresholds of two sets of odor active molecules. One
data set included 53 aliphatic alcohols. The second data set included 74 monoand di-substituted pyrazine derivatives. Each
quantitative structure-activity relationship study was executed in two steps. First, linear regression equations were developed
which modeled the Ková;ts retention indices of both sets of compounds on two stationary phases, OV-101 and Carbowax-20M, with
excellent diagnostic statistics (R > 0.99). Those results were critical in the second phase of each study which was the development
of linear regression equations to calculate the logarithm of the odor threshold of the compounds (R > 0.92). One significant
feature of certain descriptors found to be important in these regression models is that they highlight the size of the molecules.
The thia-analog of ambrettolide, 1,8-oxathiacyclohexadecan-2-one (3), was synthesized from ε-caprolactone (4). Cleavage of 4 with trimethylsilyl iodide in the presence of ethanol provided iodoester 5, that was converted to the thioether 6 by treatment with tetramethylthiourea and the monoalkoxide of 1,8-octanediol. Collaud cyclization furnished the target compound 3 that contrary to thiocyclopentadecanolides 7, 8 and 9 possesses an intense musk odor.
The novel episulphides, humulene-1,2- and -4,5-episulphide and caryophyllene-4,5-episulphide, identified as components of hop oil, particularly that from hops treated with sulphur during the growing season, have been prepared under very mild conditions by the u.v.-promoted addition of sulphur to the sesquiterpenes, and have been characterised largely by i.r. and 1H n.m.r. spectroscopy.
Treatment of allylic alcohols with thiophosgene and pyridine gives thiolo chloroformates directly at room temperature, presumably via very rapid [3,3] sigmatropic rearrangements of thiono chloroformates. Synthesis of allyl thiono chloroformate from allyl alcohol, sodium hydride and thiophosgene at low temperature and warming up to room temperature supports this finding.
The formation of 2-alkenyl alkyl sulfides from S-(2-alkenyl) S-alkyl dithiocarbonates with extrusion of COS was found to be effectively catalyzed by Lewis acids. The ab initio calculations strongly suggested that the reaction falls into category of “retro-alkylthio-ene” reaction.
On the Reaction of Hydrogen Chloride with Pinenes
syn-Addition of DCI to the less hindered site of α- and β-pinene (1, 2) is demonstrated by a combination of 13C- and 2H-NMR spectroscopy. The resulting tertiary chloride is configurationally pure and isomerizes to bornyl chloride only. The rapidity of the isomerization with the possible conversion of a tertiary to a secondary carbocation is rationalized by strain calculations with a molecular mechanics force field.
A gas chromatographic investigation of the volatile part of a pineapple concentrate led to the identification of 59 substances, 35 of which were not previously found in pineapple. The identifications and syntheses of some esters (Δ3- and Δ4-unsaturated, β-hydroxy, β-acetoxy, and δ-acetoxy) and of a new sulfur compound are given.
4-Methyl-5-(β-hydroxyethyl)-thiazole has been isolated from cocoa. This practically inodorous substance is accompanied by trace amounts of its dehydration product, 4-methyl-5-vinyl-thiazole, possessing a strong nut-like odour. The RMN. and MS. spectra of the latter are described.
In two communications “On some Astringent Substances as sources of Pyrogallic Acid,” read before the London Chemical Society in the years 1842, 1843, I showed that the usual division of the varieties of tannin into two genera—to wit, those which give black, and those which give green precipitates with salts of iron,—though called in question by Berzelius, is still well-founded : and likewise, that these two genera consist of a great variety of species, which, though closely resembling each other in properties, are still dissimilar in nature ; the only instances in which the same species of tannin had been procured from two different plants, being those of nut-galls and sumach. Professor Strecker’s important observation made some seven years ago, that grape-sugar is produced when the tannin of gall-nuts is boiled with dilute sulphuric acid, seemed to render a further examination of the varieties of tannin desirable.
A concentrate of the volatile flavor of yellow passion fruit (Passiflora edulis f. flavicarpa) has been prepared. Investigation by gas liquid chromatography and mass spectrometry led to the identification of 165 compounds, 161 of which were not previously found in passion fruit. Some of these substances are new naturally occurring flavor compounds.
Steam-distilled hop oils (from hops dressed on the bine with sulphur) have been shown to contain 3-(4-methylpent-3-enyl)thiophen (2) and 4-(4-methylpent-3-enyl)-1,2-dithiacyclohex-4-ene (4) together with the corresponding trisulphide (5) and tetrasulphide (6) but not the monosulphide (3). All five compounds are obtainable from myrcene (1) and sulphur and have been characterised, and some alternative syntheses and related work are described.
In addition to the previously described stereoisomers of 8-mercapto-p-menthan-3-one about 120 further constituents have been identified in Buchu leaf oil of commercial origin. Some new sul furated terpenoid ketones as well as p-menthan-3-one derivatives oxygenated in the 2 or 4 position found for the first time to occur in nature are discussed in more detail.
Several hundred species of neotropical plants are pollinated by glossophagine bats¹,². These bats use their highly developed sonar system for orientation, so we might expect bat-pollinated flowers to have evolved acoustically conspicuous structures to make them easier to detect. We find that the bat-pollinated neotropical vine Mucuna holtonii directs its echolocating pollinators to its flowers by means of an acoustic nectar guide. The flower contains a small concave ‘mirror’ that works like an optical cat's eye, but in the acoustic domain, reflecting most of the energy of the bats' echolocation calls back into the direction of incidence.
Three flavor-active volatile thiols (4-mercapto-4-methylpentan-2-one, 4-mercapto-4-methylpentan-2-ol and 3-mercaptohexan-1-ol) involved in Vitis vinifera L. var. Sauvignon blanc wine aroma can be generated in vitro from nonvolatile must extracts by the enzyme action of a cell-free extract obtained from the gastrointestinal bacterium Eubacterium limosum. The specificity of a cysteine conjugate β-lyase (EC 4.4.1.13) which is contained in the cell-free extract, strongly suggested the existence of precursor for these volatile thiols having a structure of S-cysteine conjugate. Gas-phase chromatography analysis coupled with mass spectrometry of must extract in the form of trimethylsilylated derivatives, verified this hypothesis. The release of flavor-active volatile thiols during alcoholic fermentation of the must is shown to be due to the degradation, by yeast, of the corresponding S-cysteine conjugates. This mechanism explains the amplification of the typical Sauvignon blanc grape aroma during alcoholic fermentation. Keywords: Cysteine conjugate β-lyase; Eubacterium limosum; flavor precursor; metal ion chelated column; Sauvignon blanc; S-cysteine conjugate; varietal aroma
The use of a new technique combining low-temperature vacuum distillation with a specific chemical capture with an organomercuric compound enabled the extraction of volatile odorous thiols present at very low concentrations in the Bordeaux red wine varieties Merlot and Cabernet Sauvignon. The analysis of wine extracts by gas chromatography coupled with detection by olfactometry, flame photometry, and mass spectrometry led to the identification of three aromatic thiols: 3-mercapto-2-methylpropanol, identified for the first time in wine; 3-mercaptohexanol; and 3-mercaptohexyl acetate, already described in Sauvignon Blanc wines. Keywords: Vacuum distillation; p-hydroxymercuribenzoate; aroma; 3-mercapto-2-methylpropanol; 3-mercaptohexanol; 3-mercaptohexyl acetate; Bordeaux red wines; Cabernet Sauvignon; Merlot
γ-Thiolactones [5-alkyldihydro-2(3H)-thiophenones] and δ-thiolactones (6-alkyltetrahydro-2H-thiopyran-2-ones) were synthesized via isothiouronium salts by reaction of the corresponding oxygen-containing lactones with thiourea and hydrobromic acid. The identity of the compounds was confirmed by means of IR, MS, and 1H and 13C NMR. Separation of the enantiomers of the thiolactones was achieved by capillary GC using heptakis(2,3-di-O-methyl-6-O-TBDMS)-β-cyclodextrin as stationary phase. The substitution of oxygen by sulfur induces tropical fruit notes, which are more pronounced for the δ-thiolactones. Odor thresholds are dependent on ring size and chain length. Keywords: γ-Thiolactone; δ-thiolactone; capillary GC; spectroscopic data; GC enantioseparation; odor threshold
Volatile thiols were purified from a dichloromethane extract of Sauvignon blanc wine by the reversible combination of the thiols with p-hydroxymercuribenzoate, fixation of the resulting complex in an anion exchange column, and finally release of the thiols with cysteine. By analyzing the purified thiol extract from 500 mL of wine, using gas chromatography coupled with mass spectrometry, it was possible to measure the concentrations of five volatile compounds at once: 4-mercapto-4-methylpentan-2-one, 3-mercaptohexyl acetate, 3-mercaptohexan-1-ol, 4-mercapto-4-methylpentan-2-ol, and 3-mercapto-3-methylbutan-1-ol. Analysis of 10 typical Sauvignon Blanc wines (Bordeaux, Sancerre) showed that the first three compounds listed above are expected to be involved in varietal aroma, as they may be present at concentrations greatly in excess of their respective perception thresholds. Keywords: Volatile thiol; aroma; Sauvignon blanc wine; Vitis vinifera; p-hydroxymercuribenzoate
The volatile flavor components of yellow passion fruits have been isolated using four different isolation techniques. The most representative and typical extract was obtained by vacuum headspace sampling and subsequent liquid−liquid extraction of the aqueous phase. This vacuum headspace concentrate was prefractionated by medium-pressure adsorption chromatography on silica gel. Approximately 180 components were identified in the LC fractions of yellow passion fruit flavor for the first time. Of these compounds, 14 components have not previously been reported as naturally occurring flavor ingredients. Moreover, 47 sulfur-containing volatiles were identified in yellow passion fruits after enrichment by preparative multidimensional capillary gas chromatography; 35 of these components are reported to be present in the tropical fruit flavor for the first time, and 23 of these sulfur-bearing compounds have not been previously reported as constituents of food flavors and are therefore new natural components. In addition, the enantiomeric distributions of several chiral flavor substances were determined by enantioselective multidimensional gas chromatography. Keywords: Yellow passion fruit flavor; comparison of sampling techniques; vacuum headspace method; sulfur volatiles; enantio-MDGC
The fruits of three varieties of Indonesian durian have been analyzed by GC-MS and flavor dilution analysis. Twenty-four of the 43 peaks that contributed to the flavor of the 5× diluted extract, as detected by sniff−GC, had a sulfury note. Upon diluting the original extract 50 times, 11 components of the 17 which could still be detected by sniff−GC had a sulfury note, 3 of which were especially strong. One of the three strongest durian odorants was identified, based on Kovats index, MS, and odor description, as 3,5-dimethyl-1,2,4-trithiolane. Ethyl 2-methylbutanoate was found to have the highest odor impact among the non-sulfurous odorants in durian. Keywords: Durian; tropical fruit; aroma dilution analysis; fruit flavor; S-ethyl thioacetate; 3,5-dimethyl-1,2,4-trithiolane
A sensitive method for detecting volatile sulfur compounds was used to determine sulfur compounds in vapors above orange and grapefruit juices. Hydrogen sulfide and methyl sulfide were found in all samples; SO2, COS, MeSH, and some higher alkyl sulfides were detected in some. Of all these, only hydrogen sulfide has been reported as a constituent of orange and grapefruit juices. Since hydrogen sulfide and methyl sulfide were found in the parts-per-billion concentration range, levels which are above their reported aroma thresholds in air, they probably contribute to the flavor of fresh orange and grapefruit juice.
A series of mono-, di-, and trisubstituted thiazoles containing alkyl, alkoxy, and acetyl functional groups was synthesized and their mass spectra, gc retention indices (IE values), and organoleptic properties were determined. Significant flavor correspondence was found between the thiazoles and derivatives of pyrazine and pyridine possessing comparable functional groups. These similarities tended to be greater with the 2- and 4-substituted thiazoles than the 5-substituted thiazoles, which were more sulfury in character. The variations in odor quality in these N- containing heterocycles are discussed-in terms of structure and charge distribution.
New information is presented concerning the chemistry of flavor relative to the processing of orange juices. Capillary column-flame ionization (FI) and dual channel FI and electron-capture (EC) detection systems with programmed temperature gas chromatography (PTGC) were used. Analyses were conducted on cold-pressed orange oils, centrifuged juice oils, orange juice emulsions obtained by direct centrifugation of freshly extracted juices, and concentrated aqueous orange essences obtained by vacuum recovery from fresh juices. The complex chemical spectra exhibited by each of these materials showed differences dependent on their sources, whether from the peel or juice of the orange, and also on the method of recovery. Electron-capture responses shown by each flavor enhancement material were related principally to its oxygenated fractions and were more intense in the juice-oriented materials. It was indicated that components giving EC response were related to the fresh aroma factors in the juice, possibly providing secondary flavor characteristics.
The "penetration and puncturing" theory of olfaction explains quantitatively the olfactory threshold of different types of molecules, but the quality of the odor has proved more difficult to measure and to interpret in fundamental terms. This theory predicts that rates of desorption and molecular cross-sectional areas should be of primary importance. The present work tests the theory as applied to the musk odor, using more than 50 compounds representing most known groups possessing strong musk odor as well as closely related structures with weak or no muskiness. The study confirms the correlation between musk odor intensity and desorption rate and molecular dimensions and shows that chemical type is not important. The compounds were evaluated for odor strength by a panel of expert perfumers. The muskiness predicted by the theory corresponded to these evaluations, all good musks having standard desorption rates in the range 0.4 to 1.7, molecular cross sections of 40 to 57 sq. A., and ratios of 2.8 to 3.3 of length to breadth of the molecule.
Volatile products formed during the heating (135 °C) of thiamin in water and propylene glycol were examined. Carbonyls, furans, thiophenes, thiazoles, dioxolanes, and other sulfur-containing compounds were identified. Quantitatively and qualitatively greater amounts of compounds were identified in the water system. Qualitative comparisons of systems studied were made.
Ethyl 3-mercaptopropionate was isolated and identified for the first time in Concord grape by combination gas chromatography-mass spectrometry analysis. At low concentration this compound possesses high-quality Concord grape aroma and flavor.
In relation to the attraction of certain insect pests the volatile components of honeydew melon have been reinvestigated. Volatiles were isolated both by Tenax adsorbent trapping and by vacuum steam distillation continuous extraction. Major aroma compounds identified that had not been previously reported in melons include (2)-6-nonenyl acetate, (Z,Z)-3,6-nonadienyl acetate, (Z)-3-nonenyl acetate, 3-methyl-2-butenyl acetate, and ethyl (methylthio)acetate (CH3SCH2COOEt). Odor threshold determinations indicted that (Z)-6-nonenyl acetate could be an additional important contributor to the total aroma for humans.
A gas chromatographic-mass spectrometric study of the porous-polymer trapped volatiles from Dendrobium superbum Rchb. f. were examined by GC-MS, because the blossoms are attractive to the male melon fly Dacus cucurbitae Coq. Twenty-five components, mostly methyl ketones and 2-alkyl acetates, were identified. 4-Phenylbutan-2-one, structurally related to the known male melon fly attractants 4-(p-acetoxyphenyl)butan-2-one ("cue-lure") and 4-(p-hydroxyphenyl)butan-2-one, was found, but the two known attractants could not be detected. The major components of the trapped volatiles are ethyl acetate and 2-tridecanone.