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Pyridyl-Substituted Alkamine Ethers as Antihistaminic Agents
... 8 Picolinamide (2-pyridinecarboxamide) (2), nicotinamide (3-pyridinecarboxamide) (3), and isonicotinamide (4-pyridinecarboxamide) (4) are a class of medicinal agents with wide range of chemical and biological applications. [9][10][11] Nicotinamide is a part of the pyridine nucleotides as NADC and NADPC that plays a vital role in biological oxidative chemistry and is essential for the human body system. [12][13][14][15][16] Isonicotinamide has strong antipyretic, antitubercular, fibrinolytic and antibacterial activities. ...
... (4-methylbenzoyl)picolinamide(10) and 3-(4-methylbenzoyl)isonicotinamide (11) : 10 and 11 were synthesized from nicotinic acid (5) according to the literature procedure. 20 1 H-NMR and13 C-NMR spectra for carboxamides (10 and 11) are in agreement with the literature values.20 ...
We aimed the synthesis of carboxamide 8 and 10, however, beside the main product, one more species was detected in the reaction solution. The characterization of this side product showed that it was the other isomer of the main product. To establish reaction conditions for the synthesis of carboxamide derivatives, we have set up several experiments by changing the Fe2+ stoichiometry. When a molar equivalent Fe2+ was used, only two reaction products 8 and 10 were obtained. The increase in Fe2+ stoichiometry caused the formation of side product 9 and 11 even formation of reduced alcohol products (12-15) by Minisci reaction.
... The structures of the alcohols were elucidated using IR (Infrared spectrometry), NMR (Nuclear Magnetic Resonance spectrometry) and MS (Mass Spectrometry) (see Section 3). Compared to Sperber et al.'s [28] yield (14.5%), our yield for 5 is far better. They reacted picolinic acid and benzophenone (1:6) in p-cymene solvent for about 6 h. ...
Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H2IMes)(O^N)(=CHPh), where O^N = 1-(2′-pyridinyl)-1,1-diphenyl methanolato, 1-(2′-pyridinyl)-1-(2′-chlorophenyl),1-phenyl methanolato, 1-(2′-pyridinyl)-1-(4′-chlorophenyl),1-phenyl methanolato and 1-(2′-pyridinyl)- 1-(2′-methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts showed high stability, selectivity and activity in 1-octene metathesis compared to the Grubbs first and second generation precatalysts. The 2-/4-chloro- and 4-methoxy-substituted pyridinel alcoholato ligand-containing ruthenium precatalysts showed high performance in the 1-octene metathesis reaction in the range 80-110 °C. The hemilabile 4-methoxy-substituted pyridinyl alcoholato ligand improved the catalyst stability, activity and selectivity for 1-octene metathesis significantly at 110°C.
... Doxylamine succinate having chemical name N,Ndimethyl-2-[1-phenyl-1-(pyridine -2-yl)ethoxy] ethanamine succinate is an antihistamine of the ethanolamine class [1], used as sleep inducing drug and in the therapeutic formulation of Bendectinem as an anti-nausea agent taken by pregnant women [2]. Literature review revealed that Nathan et al [3] developed method for synthesis of Doxylamine using 2-acetylpyridine and bromobenzene with magnesium turning to generate insitu Grignard reagent in presence of anhydrous ether followed by reaction with 2-dimethylaminoethyl chloride using sodamide as strong base in xylene. Charles et al [4] reported preparation of Doxylamine succinate salt by treating doxylaminen base with succinic acid in isopropyl alcohol. ...
Described herein is an improved synthesis of N,N-dimethyl-2-[1-phenyl-1-(pyridine-2-yl)ethoxy]ethanamine succinate (1). The synthesis comprises steps i) reacting compound of 2-acetylpyridine and bromobenzene in presence of magnesium turning, tetrahydrofuran and toluene solvents to obtained 2-pyridylphenylmethyl carbinol HCl (4) ii) reacting compound 4 with 2-dimethylaminoethyl chloride hydrochloride in presence of potassium hydroxide and toluene solvent to obtained N,N-dimethyl-2-[1-phenyl-1-(pyridine-2-yl)ethoxy]ethanamine (6) and iii) treatment of compound 6 with succinic acid in acetone solvent to obtain 1. The present work provides safe, robust and commercial viable manufacturing process for the synthesis of 1 having purity ≥ 99.5%.
... The substrate scope of 2-pyridylmethyl ethers was next explored (Table 3) with electron-donating 4-bromo-N,N-dimethylaniline (entries 1-4) and with 1-bromo-4-uorobenzene (entries [5][6][7][8][9]. In general, all the 2-pyridylmethyl alkyl or aryl ethers exhibited 80-92% yield and excellent selectivity, with no [1,2]-Wittig product observed by 1 H NMR of the crude reaction mixtures. ...
Control of chemoselectivity is one of the most challenging problems facing chemists and is particularly important in the synthesis of bioactive compounds and medications. Herein, the first highly chemoselective tandem C(sp (3))-H arylation/[1,2]-Wittig rearrangement of pyridylmethyl ethers is presented. The efficient and operationally simple protocols enable generation of either arylation products or tandem arylation/[1,2]-Wittig rearrangement products with remarkable selectivity and good to excellent yields (60-99%). Choice of base, solvent, and reaction temperature play a pivotal role in tuning the reactivity of intermediates and controlling the relative rates of competing processes. The novel arylation step is catalyzed by a Pd(OAc)2/NIXANTPHOS-based system via a deprotonative cross-coupling process. The method provides rapid access to skeletally diverse aryl(pyridyl)methanol core structures, which are central components of several medications.
Chiral 1,2-dihydropyridines represent a class of versatile building blocks that can undergo diversifying reactions of conjugated dienes such as reduction or cycloaddition reaction, allowing facile synthesis of chiral piperidines and other nitrogen-containing heterocycles, prominent structural motifs in drugs and bioactive compounds. The efficient synthesis of chiral 1,2-dihydropyridines is highly desirable and beneficial for the drug discovery and development. The chiral pool strategy and chiral auxiliary based synthesis require the use of stoichiometric chiral reagents, so it is much sought-after to develop catalytic asymmetric methods to synthesize structurally diverse chiral 1,2-dihydropyridines. Since the pioneering catalytic enantioselective addition of nucleophiles to the C2 position of achiral activated pyridine derivatives in 2004, this strategy has been successfully employed for the catalytic synthesis of optically active 1,2-dihydropyridines bearing an aryl, alkyl or alkynyl group at the C2 position. Recently, tandem sequences was reported based on the asymmetric conversion of C=N bonds as an emerging strategy for the synthesis of multisubstituted chiral 1,2-dihydropyridines. This review summarizes the advances in this field, and discusses the challenges and synthetic opportunities for future development. © 2021 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Background:
The preparation and use of pyridinyl alcohols as ligands showed incredible increment in the past three decades. Important property of pyridinyl alcoholato ligands is their strong basicity, which is mainly due to the lack of resonance stabilization of the corresponding anion. This strongly basic anionic nature gives them high ability to make bridges between metal centers rather than to bind to only one metal center in a terminal fashion. They are needed as ligands due to their ability to interact with transition metals both covalently (with oxygen) and hemilabile coordination (through nitrogen).
Objective:
The review focuses on the wide application of α-pyridinyl alcohols, α,α'-pyridine diols, α- bipyridinyl alcohols, and α,α'-bipyridine diols as structure motifs in the preparation of important organic molecules which is due to their strongly basic anionic nature.
Conclusion:
It is clear from the review that in addition to their synthetic utility in the homogeneous and asymmetric catalytic reactions, the preparation of the crown ethers, cyclic and acyclic ethers, coordinated borates (boronic esters), pyridinyl-phosphine ligands, pyridinyl-phosphite ligands, and pyridinyl-phosphinite ligands is the other broad area of application of pyridinyl alcohols. In addition to the aforementioned applications they are used for modeling mode of action of enzymes and some therapeutic agents. Their strongly basic anionic nature gives them high ability to make bridges between metal centers rather than to bind to only one metal center in a terminal fashion in the synthesis of transition metal cluster complexes. Not least numbers of single molecule magnets that can be used as storage of high density information were the result of transition metal complexes of pyridinyl alcoholato ligands.
The simpler properties of a number of pyridine aldehydes are recorded in Table 6.1. Spectra and ionization constants have been mentioned before (pp. 129, 142, 146; see also below).
Entsprechend dem Antagonismus von Sympathicus und Parasympathicus wirken die sympatholytischen Stoffe im Endeffekt ähnlich wie die Parasympathomimetica. Umgekehrt zeigen sympathomimetische Verbindungen ähnliche Wirkung wie die Parasympatholytica. Grundkörper für die Parasympatholytics ist das Atropin, für die Sympathomimetics das Adrenalin, sodaß beide in mancher Hinsicht ähnliche Wirkungen auslösen. Analog wirken die sympatholytischen Secale-Alkaloide mitunter ähnlich dem parasympathomimetischen Cholin. Diese Analogie läßt sich jedoch nicht verallgemeinern.
An important challenge in Cα-heteroarylation of ethers is the requirement of a large excess amount (used as solvents in many cases) of ethers to achieve effective transformations. This drawback has significantly restricted to the use of simple and easily accessible ether substrates. To overcome this limitation, a new, efficient N-hydroxy succinimide (NHS) mediated mild and metal-free CDC strategy for direct Cα-heteroarylation of diverse ethers has been developed. Different from our previous benzaldehyde mediated photoredox Cα-heteroarylation, we have identified NHS as a new efficient mediator without using light. A distinct non-photoredox engaged hydrogen-atom-transfer (HAT) mechanism by a nitrogen-centered radical cation produced from NHS is initially revealed. Notably, Only 5-10 equivalents of ethers as coupling partners are used, which allows for structurally diverse and complex ethers to engage in this process to create highly medicinally relevant Cα-heteroarylated ethers. Furthermore, more structurally diverse hetereocyclics can serve as reactants for this process.
Other than their valuable use as starting materials and intermediates in the synthesis of drugs and other important organic compounds, pyridinyl alcohols are largely used as hemilabile chiral chelating ligands in the development of homogeneous transition metal catalysts. The pyridinyl alcohols covered in this review are divided into four types based on the position of the alcohol group and number of the pyridine ring, namely alpha-pyridinyl alcohols alpha,alpha '-pyridine diols, alpha-bipyridinyl alcohols and alpha,alpha '-pyridine diols. Many synthetic procedures have been conducted by a number of research groups in order to obtain the best synthetic method for these alcohols in the past decades. Significant and remarkable efforts, by many chemists, have been made to synthesise enantiomerically pure pyridinyl alcohols in very good to excellent chemical and optical yields. In this article, a critical overview of the synthetic strategies of the aforementioned pyridinyl alcohols with detailed procedures is provided with the aim of giving a wide scope for the reader in this area.
The history of the discovery of pyridine and of the development of its structure was outlined in Chapter 1, and its general character as an aromatic compound, as shown in its geometry and stability, was discussed in Chapter 2. The molecular dimensions of three important pyridine derivatives, 2-pyridone1a, 2-pyridthione1b, and nicotinic acid1c are indicated in the skeletons (1), (2), and (3). Data are available for pyridine hydrochloride2a, 1-hydroxypyridinium chloride2b, 4-nitropyridine 1-oxide3a and trans-4,4′-azopyridine 1,1′-dioxide3b.
In this Chapter a survey and discussion of the chemistry of compounds which antagonize the effects of histamine at H1 receptors are presented. Ellis (1969) has compiled an extensive list of reviews on histamine, 5-hydroxytryptamine, and their antagonists, several of which include some account of the chemical aspects of antihistaminics. Here, attention is drawn in particular to the reviews of Witiak (1970), Doerge (1971), and Melville (1973); an extensive review of earlier work is available in Czech (Protiva, 1955). Developments in the field are presented periodically in Annual Reports in Medicinal Chemistry sponsored by the Division of Medicinal Chemistry of the American Chemical Society, e.g. Tozzi (1972).
The oxidative cyclisation of 3-oxopropanenitriles 1a-g with alkenes 2a-c containing 2-thienyl group by manganese(III) acetate was studied. Treatment of 3-oxopropanenitriles 1a-d with 2-[(E)-2-phenylvinyl] thiophene 2a gave 4-phenyl-5-(2-thienyl)-4,5-dihydrofuran-3-carbonitriles 3a-d in moderate yields (52%-60%). 5-(2-thienyl) substituted 4,5-dihydrofuran-3-carbonitriles 3e-i were obtained by the oxidative cyclisation of these 3-oxopropanenitriles with 2-[(E)-1-methyl-2-phenylvinyl]thiophene 2b in good yields (54%-68%). In addition, the reactions of 2-(1-phenylvinyl)thiophene 2c with various 3-oxopropanenitriles produced 4,5-dihydrofurans 3j-n containing heterocycle in 77%-91% yields.
Pyridinethiols and PyridinethionesPyridylalkylthiolsPyridyl ThioketonesPyridyl SulfidesPyridylalkyl SulfidesPyridyl DisulfidesPyridyl SulfoxidesPyridyl SulfonesPyridylalkyl SulfonesPyridinesulfinic AcidsPyridinesulfonic AcidsPyridyldithiocarbamic Acid and Phridylalkyldithiocarboxyl Acid DerivativesThiocyanatopyridinesBiological Activity of Sulphr Compounds of PyridineSelenium Compounds of PyridineTablesBibliography
Other than their valuable use as starting materials and intermediates in the synthesis of drugs and other important organic compounds, pyridinyl alcohols are largely used as hemilabile chiral chelating ligands in the development of homogeneous transition metal catalysts. The pyridinyl alcohols covered in this review are divided into four types based on the position of the alcohol group and number of the pyridine ring, namely α-pyridinyl alcohols, α,α’-pyridine diols, α-bipyridinyl alcohols and α,α’-pyridine diols. Many synthetic procedures have been conducted by a number of research groups in order to obtain the best synthetic method for these alcohols in the past decades. Significant and remarkable efforts, by many chemists, have been made to synthesise enantiomerically pure pyridinyl alcohols in very good to excellent chemical and optical yields. In this article, a critical overview of the synthetic strategies of the aforementioned pyridinyl alcohols with detailed procedures is provided with the aim of giving a wide scope for the reader in this area.
5-Methyloxazolo-(3,2a)-1′,4′-dihydro-4′-quinolinone and traces of skatole are respectively formed when N-acetonylanthranilic acid is heated with acetic anhydride and with ethylene glycol.
A series of l-methyl-2-hydroxyiminomethyl-aryl-pyridinium salts has been prepared, as new potential antidotes of poisoning by organo-phosphorus compounds. Several synthetic sequences were tested and all but one, with an internal branch, rejected because they were judged inconvenient and/or because of low yields. 2-Picoline was oxidized to picolinic acid and this converted to 2-(4-X-benzoyl)pyridines either via decarboxylation followed by nucleophilic addition to selected aromatic aldehydes and oxidation of the secondary alcohols thus obtained or by conversion to picolinoyl chloride followed by Friedel-Crafts reactions with selected mono-substituted arenes. The 2-aroyl-pyridines were then converted to the corresponding oximes (E and Z forms in some cases), followed by methylation of pyridine nitrogen.
The easily synthesis of dihydrofuronaphthoquinones and C-alkenylated naphthoquinones has been investigated through the radical oxidative cyclization of 2-hydroxy-1,4-naphthoquinones and thiophene or furan substituted alkenes catalyzed by manganese(III) acetate. The corresponding heteroaryl substituted dihydrofurans and naphthoquinones have been isolated in good yields.
An efficient and simple method for the synthesis of various [1, 2, 3]triazolo[1, 5-a]pyridines has been established. The method involves a copper(II)-catalyzed oxidative NN bond formation that uses atmospheric oxygen as the terminal oxidant following hydrazonation in one pot. The use of ethyl acetate as the solvent dramatically promotes the oxidative NN bond-formation reaction and enables the application of oxidative cyclization in the efficient one-pot reaction. A mechanism for the reaction was proposed on the basis of the results of a spectroscopic study.
Cleavage of the siliconcarbon bond of 2-(trimethylsilyl)pyridine has been affected by benzoyl chloride, phthalic anhydride, and ethyl chloroformate as well as benzaldehyde to provide a novel pathway to heterocyclic ketones, keto-acids, esters and alcohols. A cyclic four-membered transition state is proposed in which the polarity of both the siliconaromatic bond and the attacking reagent are stressed.
The syntheses of five optically active α-aryl-2-pyridylmethanols 1–5 are described. It is shown by means of chemical correlation with the known (−)-(αR,2S)-α-phenyl-2-piperidylmethanol 6 that all levo-rotatory isomers of 1–4 are of R configuration. It is also found via the relative integral intensities in the infrared spectra of the bands due to free and intramolecularly bonded hydroxyl groups in the compounds 1–4 and the free hydroxyl groups in the model compounds 7–10, that the population of the conformers with an intramolecular OH···N bond in compounds 1–4 exceeds 80%.
A series of substituted dialkylaminoalkanes have been synthesized by various methods and tested as histamine antagonists. Two compounds, γ-phenyl-γ-(2-pyridyl)-N,N-dimethylpropylarnine and γ-(p-chlorophenyl)-γ-(2-pyridyl)-N,N-dimethyl-propylamine, have been found to be effective clinically. In general the most active compounds were derivatives of N,N-dimethylpropylamine, having a 2-pyridyl and a phenyl, para-substituted phenyl or heterocyclic group in the gamma position.
A series of chiral 1,3-aminoalcohols derived from cis-(1R,2S)-2-benzamidocyclohexanecarboxylic acid were synthesized and applied to the enantioselective arylation of aromatic aldehydes. The reactions exhibited good yields (up to 90%) and moderate to high enantioselectivities (up to 99%). Not only the enantioselectivity but also the stereochemistry of the product were controlled by the substituent effect of the chiral ligands.
The catalytic enantioselective arylation of aryl aldehydes using boronic acids as the source of transferable aryl groups is described; the reaction is found to proceed in good yields and in good to high enantioselectivities (up to 99% ee) in the presence of a chiral aminophenol ligand.
Asymmetric aryl transfer of triphenylboroxin to a set of aryl aldehydes has been carried out in the presence of chiral amino alcohols derived from (S)-proline with high enantioselectivity. Substituted phenyl boroxins were also used as aryl source in asymmetric arylation of benzaldehyde.
4,5-Dihydrofuran-3-carbonitriles 3a–i were obtained through oxidative cyclizations of 3-oxo-3-phenylpropanenitrile 1a, 3-oxo-3-thien-2-ylpropanenitrile 1b, 3-(2-furyl)-3-oxopropanenitirle 1c, 3-(1-benzofuran-2-yl)-3-oxopropanenitrile 1d, and 4,4-dimethyl-3-oxopropanenitrile 1e mediated manganese(III) acetate with 1,1-diphenyl-1-butene 2a and 1,2-diphenyl-1-pentene 2b. The treatments of these 3-oxopropanenitriles with 2-thienyl substituted alkenes such as 2-[(E)-2-phenylvinyl]thiophene 2c, 2-[(E)-1-methyl-2-phenylvinyl]thiophene 2d, and 2-(1-phenylvinyl)thiophene 2e formed 5-(2-thienyl)-4,5-dihydrofuran-3-carbonitriles 3j–r in good yields (45–93%). As a result, 2-thienyl substituted alkenes formed products in higher yields than phenyl substituted derivatives.
Naphthalene catalysed reductive lithiation of various chloroazines (1, 7, 10, 13) in the presence of different electrophiles yields, after hydrolysis, the expected functionalised heterocycles with one (2, 8), two (11, 14a–d) and three nitrogen atoms in the ring (14e,f). This methodology allowed us to trap in situ the lithium imine derived from the reaction of 2-pyridyllithium with benzonitrile, by reaction with a Grignard reagent in the presence of titanium alkoxides. 2,4-Dimethoxypyrimidines (14a,c,d) are demethylated under acidic conditions to give the corresponding uracil derivatives 16.
Hydroxymethyl, aminomethyl, carboxyl, methoxycarbonyl, carbamoyl, hydrazinocarbonyl, formyl, vinyl and phenyl groups attached to various positions of a pyridine ring were reduced at a mercury cathode in an aqueous sulfuric acid solution. These groups, except for the phenyl group, at the 2- and 4-positions could be reduced, while the reduction of the groups at the 3-position seemed to be difficult. The reduction potential of the groups at the 4-position was generally less negative than that of the same group at the 2-position. Current efficiencies for the reduction of hydroxymethyl, aminomethyl and vinyl groups were higher in the case of 4-substituted-pyridines than 2-substituted-pyridines, while this tendency reversed in the case of the other groups. An obvious steric hindrance effect on the current efficiency was also observed in the reduction of substituted-hydroxymethyl groups attached to the 2-position. On the basis of these results, reduction mechanism is discussed and also the synthetic scope is described.
2-Pyridinmethanole mit aliphatischen oder aromatischen Substituenten am α-C-Atom spalten nach Methylierung des Pyridinstickstoffes beim Erhitzen in wäßrig-alkalischem Medium die Seitenkette als Ketone bzw. Aldehyde ab. α-Phenyl-2-pyridiniummethanol ist am α-C-Atom methylierbar.
The Alkali-Catalyzed Cleavage of 2-Pyridiniummethanols
N-Methylated 2-pyridinemethanols with aliphatic or aromatic substituents at the α-C-atom are cleaved into ketones or aldehydes when heated with aqueous alkalihydroxide. α-Phenyl-2-pyridiniummethanol can be methylated at the α-C-atom.
Es wird die Darstellung von Dimethylamino-, Piperidino- und α-Pipecolino-äthyläthern einiger α-substitutierter Benzylalkohole beschrieben. Die hergestellten Verbindungen besitzen alle Antihistamin und spasmolytische Wirkung. Ihre Antihistaminwirkung steht etwas hinter derjenigen des Benadryls zurück, während die antagonistische Wirkung gegen Acetylcholin-Spasmen von der gleichen Grössenordnung ist wie diejenige des Benadryls.
Doxylamine succinate, N,N-dimethyl-2-[1 -phenyl-1-(2-pyridinyl)-ethoxy]ethanamine succinate is an antihistamine used primarily as a sedative. Carbon-14 labeled doxylamine succinate, required for toxicological studies, was synthesized in two steps starting from 2-benzoyl pyridine.
Syntheses of the three isomeric 2,3-dihydro-7-nitro-5-(2-, 3-, and 4-pyridyl)-1H-1,4-benzodiazepines from the corresponding (2-chloro-5-nitrobenzoyl)pyridines and ethylenediamine are described. The required benzoyl-pyridines were made by nitration of the appropriate (2-chlorobenzoyl)pyridines, the preparations of which are given. The 7-nitrobenzodiazepines were converted, by reduction of the nitro-group followed by the Sandmeyer reaction, into the corresponding psychopharmacologically active 7-chloro-derivatives.
Reaction of 2-pyridylmagnesium chlorides with N,N-dialkyl arylamides afford exclusively 2-(aroyl) pyridines in high yields and purity without the formation of any tertiary alcohol. This method employs easily available raw materials and avoids the use of hazardous lithium reagents and cryogenic conditions. Further, preferential reactivity of this Grignard reagent with N,N-dialkyl arylamides over its carbonitrile counterparts offers a variety of 2-(aroyl) pyridines including the ones containing carbonitrile groups on the aryl ring.
Reactions of 3-α-chlorobenzylpyridazine (4) with alkoxides have been found to yield 6-substituted or 4-substituted 3-benzylpyridazines (7a–c, 8a–c) rather than the usual ethers (6a–c). Introduction of an electron-donating substituent into the 6-position of the pyridazine nucleus of 4 has been shown to suppress such telesubstitution processes. With phenyl-3-pyridazinylmethanol (3), thermally induced dismutation affording 3-benzylpyridazine (17) and 3-benzoylpyridazine (11) has been observed.
General Biological EffectsAntihistamine CompoundsPressor CompoundsLocal AnestheticsHypnotiaAntifebrides and AnalgesicsAntipasmodicsAnticonvulsantsGermicidesAnalogs of DDTMiscellaneous Compounds and Their Properties
PreparationPropertiesReactionsDihydric and Polyhydric Alcohols Containing One Pyridine NucleusDihydric Alcohols Containing Two Pyridine NucleiSide-Chain Hydroxyacid DerivativesDerivatives Containing Both Nuclear and Side-Chain HydroxylTablesBibliography
Allergic reactions cause a number of acute and chronic diseases. The antigen or allergen causing the allergic reaction is usually a protein, a polysaccharide, or a low molecular mass compound (hapten) bound to an endogenous protein. Antigens induce the synthesis of antibodies, which are serum proteins, referred to as immunoglobulins (Igs). Antigen cross-linking of the IgE molecules leads to cellular responses involving release of preformed mediators, e.g., histamine. Antihistamines or histamine H1 receptor antagonists are used in the treatment of allergic diseases. In contrast to the first-generation or classical antihistamines the second-generation antihistamines do not have the side effects sedation, fatigue, and drowsiness. Mast cells are the predominant storage site for histamine in most tissues. Cromolyn sodium or disodium cromoglycate (DSCG) probably acts on certain types of chloride channels expressed in mast cells and sensory nerves.
The ephedrine-based diselenide appears as a new promiscuous catalyst, able to generate optically active alcohols by addition of organozinc to aldehydes (up to 97% ee), and shows powerful GPx like activity, reducing H(2)O(2) to water in only 16.33 min (eleven times faster than PhSeSePh).
A family of polystyrene-supported amino alcohols, characterized by a high catalytic activity in alkyl transfer from zinc to formyl groups has been successfully tested in the enantioselective addition of phenyl zinc reagents to aldehydes to afford chiral diarylmethanols. Enantioselectivities higher than 90% (mean ee 90.5%; eight examples) are recorded with aromatic aldehydes in what represents the first successful use of heterogeneous, polymeric reagents for enantiocontrol in the phenylation of aldehydes.
A number of triarylmethanes were prepared, the majority of which are new. One of the aryl groups is a naphthol, 1,3,5-trimethoxybenzene, or resorcinol, or an indole, pyrrole or pyridine ring. Three synthetic routes are described: (1) reaction of a benzhydrol with an electron-rich aromatic compound; (2) direct condensation of benzaldehyde or hydroxybenzaldehydes, with N,N-dimethylaniline or its derivatives and 2-naphthol; and (3) displacement of benzotriazole in benzotriazolyl derivatives by Grignard reagent according to our recently developed benzotriazole methodology.
Various substituted aryl-pyridyl ketones were hydrogenated in the presence of Ru-XylSunPhos-Daipen bifunctional catalytic system with enantiomeric excesses up to 99.5%. Upon introduction of a readily removable ortho-bromo atom to the phenyl ring, enantiomerically enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method with 97.3% ee, which provided an important chiral intermediate for some histamine H(1) antagonists.
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