Alejandro F Barrero

Alejandro F Barrero
University of Granada | UGR · Department of Organic Chemistry

PhD

About

330
Publications
23,586
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7,098
Citations
Citations since 2017
12 Research Items
1711 Citations
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300

Publications

Publications (330)
Article
The essential oil composition from the aerial parts of Ormenis africana (Asteraceae), an endemic species from Morocco, has been investigated by GC/MS. A total of 31 compounds were identified, representing 77%. After fractionation by column chromatography, the main compound was isolated and its structure elucidated by NMR spectroscopy. The essential...
Article
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Cardenolide-free extracts from Digitalis obscura showed significant antifeedant effects against the aphid Myzus persicae and this activity correlated with their phenylethanoid content. The content in phenylethanoids of Digitalis obscura has been studied. Maceration of the aerial parts of D. obscura was used for the selective extraction of the natur...
Article
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We have proven that the biomimetic-like synthesis of cannabinoids from citral and the corresponding phenolic counterpart may well be carried out using water as a solvent. The influence of different additives such as surfactants was also analyzed. Rationalization of the reaction mode and regiochemistry of the processes were provided in terms of "on...
Article
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Many terpenoids are biosynthesized after a cascade of cyclizations and rearrangements of carbocations mediated by terpenoid synthases, as exemplified in the biosynthesis of lanosterol. Although several reports of organisms or purified enzymes catalyzing this cascade of reactions in the laboratory have been described, the development of chemical tra...
Article
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Naturally occurring nootkatone, with reported insecticidal and acaricidal properties, has been used as a lead to generate molecular diversity and, consequently, new insect antifeedant and ixodicidal compounds. A total of 22 derivatives were generated by subjecting this molecule to several reactions including dehydrogenation with the iodine/DMSO sys...
Article
We have developed and rationalized a biomimetic transformation mimicking halimane-synthases based on a Lewis acid-catalyzed cascade of cyclizations plus rearrangements of epoxypolyprenes. Two rings, three stereogenic centers and a new double bond were generated in a single chemical operation. Based on this cascade transformation, we achieved a unif...
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Currently, the use of synthetic pesticides is the main method of plant protection applied in agri- and horticulture. However, its excessive use leads to the development of pesticide resistance, a contamination of the environment, toxicity to non-target organisms, and risks for human health. With the ultimate aim of contributing to the develop of a...
Article
The system I2/DMSO mediates the one-step transformation of α-isopropylidene ketones into furan rings following a biomimetic approach. This methodology has been used for the synthesis of terpene furans such as mintfurane, curzerene, atractylon and isoatractylon, all of them possessing interesting biological activities. The synthesis of linderazulene...
Article
The first total synthesis of a natural diterpene valparane, (-)-valpara-2,15-diene (1), has been achieved from all-trans-geranylgeraniol (9), a natural renewable compound. The key steps involve a Ti(III)-mediated radical cyclization of the chiral monoepoxypolyene (14R,15R)-14,15-epoxy,16-tert-butyldimethylsilyloxygeranyllinalyl acetate (8) to give...
Article
The insecticidal and acaricidal effects of the essential oils (EO) from two populations of Geranium macrorrhizum L (ornamental variety Bevan, VB and wild population from Hungary, GH) have been studied against several insect pests of economic importance in agriculture (Spodoptera littoralis, Myzus persicae and Rhopalosiphum padi), and the hard tick...
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Apocarotenoids are metabolites originated by degradation of carotenes through the loss of carbon atoms placed at the side chain of their structure as consequence of oxydative reactions. We present here the first review of apocarotenoids in the fungi mucorales Phycomyces blakesleeanus, Blakeslea trispora and Mucor mucedo. This review is divided into...
Article
Two catalytic cascade cyclization methods (radical and cationic) to obtain aromatic polycyclic diterpenes hydroxylated at C3 starting from aromatic epoxypolyprenes were developed. The catalytic use of the Lewis superacid bismuth triflate produces a good yield of cyclized 2 from epoxypolyprene 3. This research may well direct future efforts to the s...
Chapter
Over the last century, high levels of creativity and structural complexity have been achieved in the synthesis of natural products, mostly motivated by the desire to utilize the intriguing bioactivities that these molecules offer for the benefit of society. From the marine depths to the microscopic world of bacterial cultures, nature affords an end...
Article
A mild and efficient method for the reductive dehalogenation of carbon–halogen bonds in both activated (allylic or benzylic) and non-activated halides with excess Ti(III) has been developed. This synthetic method is compatible with a wide range of functional groups and reaction conditions, and thus presents a mild process for reductive dehalogenati...
Article
A mild and efficient methodology for the reductive dehalogenation of carbon‒halogen bonds in both activated (allylic or benzylic) and non-activated halides with excess Ti(III) is thoroughly described. A detailed computational and experimental study corroborates that the reaction occurs via allyl(benzyl)-radical and allyl(benzyl)–Ti, which is proton...
Article
Efficient procedures based on the use of iodine for the aromatization of a series of terpenoids possessing diene and homoallylic or allylic alcohol functionalities are described. Different examples are reported as a proof-of-concept study. Furthermore, iodine also proved to mediate the dehydrogenation of testosterone.
Article
The oxidative cleavage of β-carotene in the Mucorales produces three fragments of 18, 15, and 7 carbons, respective heads of three families of apocarotenoids: the methylhexanoids, the trisporoids, and the cyclofarnesoids (named after their 1,6-cyclofarnesane skeleton). The apocarotenoids are easily recognized because they are absent in white mutant...
Article
Several preparations were obtained from the aerial parts of predomesticated Lavandula luisieri, including the essential oil and ethanolic, hexane, and ethyl acetate extractives. Additionally, pilot plant vapor pressure extraction was carried out at a pressure range of 0.5-1.0 bar to give a vapor pressure oil and an aqueous residue. A chemical study...
Article
We describe efficient procedures based on the use of iodine for the synthesis of biaryls from arylcyclohexenols or arylcyclohexanols using sub-stoichiometric/catalytic iodine and dimethyl sulfoxide (DMSO) as oxidant. Heteroarylcyclohexanols also produced the corresponding biaryl products. It was proven that biphenyl can also be efficiently obtained...
Article
A simple method to obtain extracts enriched in bioactive limonoids from Citrus aurantium L. seeds has been developed, using solvents of increasing polarity. 1H NMR data from the extracts revealed that the highest amounts of limonoids were present in the t-butylmethylether extract. The comparison between extracts obtained from dormant and germinatin...
Article
Following the principles of collective total synthesis, a number of natural products sharing an optically pure, multifunctional, cyclopentanic core were synthesized from a common precursor: plinol A (1). This intermediate was efficiently obtained in only four steps from (-)-linalool (2) using as the key step a Ti(III)-mediated diastereoselective ra...
Article
We decided to follow the so-called “collective total synthesis” approach to synthesize several structurally different molecules from a common intermediate possessing appropriate stereochemistry and functionalities. As the common precursor for the efficient preparation of these bioactive molecules, we chose (+)-3,4-dihydro-γ-ionone (1), a natural co...
Article
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A detailed experimental and theoretical study corroborates that the reductive deoxygenation of activated (allylic or benzylic) alcohols with excess Ti(iii) proceeds via an allyl(benzyl)-radical and allyl(benzyl)-Ti, which is protonated, regioselectively in the case of allylic derivatives. The H atom of the newly formed C-H bond in the product origi...
Article
The purpose of this work is to provide spectroscopic evidence of possible chemical pathways that took place in the formation of fossil resins Class I. The natural polymerization process is mimicked in the laboratory using pure communic acids (terpene derivatives) as reactants, which were subjected to controlled temperature treatment. We shall focus...
Article
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The synthesis of a cyclohexane skeleton possessing different oxygenated functional groups at C-3, C-8 and C-9, and a D1,6-double bond has been accomplished in 10 steps with an overall 17% yield. This compound is a key intermediate for access to a wide range of compounds of the bioactive trisporoid family. The synthetic sequence consists of the prep...
Article
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ABSTRACT The essential oils obtained by hydrodistillation of scales and seeds of Cedrus atlantica Endl.Carr. were analysed byGas Chromatography-Mass Spectrometry (GC-MS). Twenty-one components representing80% of the total scales oiland nineteen components comprising 95.75% of the total seeds oil were identified. The major components in the scales o...
Article
The first total synthesis of the natural apocarotenoids (+)-apotrisporin E (1) and (+)-apotrientriols A and B has been accomplished. The structure, relative stereochemistry and the assignation of the absolute configuration have been confirmed. This is a fast and easy access to this family of natural products whose key steps are a diastereoselective...
Article
Full-text available
The first total synthesis of the natural apocarotenoids (+)-apotrisporin E () and (+)-apotrientriols A and B () has been accomplished. The structure, relative stereochemistry and the assignation of the absolute configuration have been confirmed. This is a fast and easy access to this family of natural products whose key steps are a diastereoselecti...
Article
Artemisia granatensis, an endemic endangered plant species from Sierra Nevada (Spain) has been successfully cultivated in artificial systems (plants in artificial soil and transformed in vitro roots) to generate enough plant biomass (aerial and root) to allow for its chemical and biological study and at the same time to provide with methods for the...
Article
Treatment of germacrone (1) with different electrophiles, and of its epoxy derivatives germacrone-4,5-epoxide (2), germacrone-1,10-epoxide (3) and isogermacrone-4,5-epoxide (4) with Brönsted/Lewis acids and Ti(III) , gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds correspon...
Article
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The heterocyclic C15 apocarotenoid 1 was isolated from mated cultures of the strains F986 (+) and F921 (−) of Blakeslea trispora. This new compound formed during sexual interaction is a minor constituent of the culture media and its structure was elucidated by spectroscopic data, including 2D-NMR. A plausible biosynthetic pathway involving a double...
Article
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The first synthesis of (+)-myrrhanol C (), an antitumor polypodane-type bicyclic triterpene with inhibitory activity against androgen insensitive prostate cancers, is reported herein (IC(50) 10 μmolar). A key step in our convergent synthesis of (+)-myrrhanol C and related analogues is the employment of a microbial stereo- and regioselective late st...
Article
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The chemical composition of the leaf oils are reported for Cupressus arizonica, C. benthamii and C. lindleyi from Mexico and compared to the leaf oil of C. lusitanica, introduced to Portugal in ca. 1634. The oil of C. arizonica has moderate amounts of butyl methyl ether (8.6%), a-pinene (7.6%), β-phellandrene (5.7%), umbellulone (5.4%), isophyllocl...
Article
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Communic acids are diterpenes with labdane skeletons found in many plant species, mainly conifers, predominating in the genus Juniperus (fam. Cupresaceae). In this review we briefly describe their distribution and different biological activities (anti- bacterial, antitumoral, hypolipidemic, relaxing smooth muscle, etc.). This paper also includes a...
Article
Full-text available
A simple genetic test allowed us to carry out the first systematic study of the apocarotenoids in the Mucorales. We have identified 13 apocarotenoids in the culture media of the fungus Phycomyces blakesleeanus (Mucoromycota, Mucorales). Three of these compounds were novel apocarotenoids: (2S,8R,E)-8,14-epoxycyclofarnesa-4,6,9-triene-2,11-diol (6),...
Article
An asymmetric concise total synthesis of the (+)-seco-C-oleanane 1 was accomplished. The successful route to this natural product involves as the key step a stepwise regio- and stereocontrolled catalytic radical polyene cascade cyclization from preoleanatetraene oxide (16), a process mediated by Cp(2)TiCl. The use of this single-electron-transfer c...
Article
The titanocene-mediated cyclization of suitably functionalized acyclic C10 epoxy-polyprenes leads, with moderate stereoselectivity, to high yields of functionalized terpenic cyclopentanes with three contiguous stereogenic centers. These highly functionalized cyclopentanes are useful intermediates for the synthesis of several natural compounds that...
Article
Full-text available
Mixed cultures of strains of opposite sex ("mated" cultures) of Blakeslea trispora contain trisporic acids and other apocarotenoids, some of which mediate the sexual responses of this fungus and other Mucorales. In mated cultures of the wild-type strains F986 and F921 we identified eleven apocarotenoids: two C(18) trisporoids, three C(15) compounds...
Article
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The chemical composition of the essential oils obtained by hydrodistillation of stem bark and leaves of Drimys winteri J.R. et G. Foster var. chilensis /DC A. Gray (Winteraceae) from Chiloe Island (ID) and Continental Chile (Santiago) (CD) were studied by GC and GC/MS. Sesquiterpene hydrocarbons constituted the main chemical groups in the stem bark...
Article
An easy procedure to obtain extracts enriched in trixagol monomalonylesther (1) from aerial parts of the plant Belladia trixago chemotype Trix was developed. Preparation of (+)-dihydro-gamma-ionone (4) was carried out directly from the extracts with good yields by selective oxidation. Other interesting odorant products as alpha-ambrinol (5), ambral...
Article
As a result of a combined theoretical and experimental study, we describe a two-step protocol for the preparation of an optically pure, multifunctional, cyclopentanic core shared by a number of natural products. This process is based on a hitherto unreported Ti(III)-mediated diastereoselective cyclization in which the hydroxy-directed template effe...
Article
Full-text available
Highly efficient preparations of anticancer β-elemene and other bioactive elemanes were carried out using the natural product germacrone as a renewable starting material. The syntheses were achieved in only 3-5 steps with excellent overall yields (43-54%). An enantioselective approach to these molecules is also described.
Article
The title compounds are interesting candidates for antifungal screening. This paper describes the enantiospecific synthesis of these compounds starting from (+)-costunolide isolated from a commercially available extract. We used two novel reactions as key synthetic steps in this work: the acid-induced cyclization of an δ,e-epoxy ester, which stereo...
Article
The syntheses of the terpenoid antifungal LL-Z1271α and other related compounds were achieved starting from the communic acids. The synthetic approach includes a mercuriation-demercuriation reaction of a γ,δ-unsaturated methyl ester in the presence of O2, giving rise to a lactone ring.
Article
Full-text available
Two new 7-carbon compounds, 1 and 2, have been found in the culture medium of Phycomyces blakesleeanus. A genetic test showed that they derive from beta-carotene. These new molecules represent the missing link that proves that beta-carotene is split into fragments of 18, 15 and 7 carbon fragments, each head of a separate family of apocarotenoids.
Article
The synthesis of a series of pyrrole and imidazole retinoids is reported. The compounds were obtained by means of reactions of phosphoranes or phosphonates with aldehydes. Several of these retinoids were evaluated against different tumor systems and some were found to have an activity comparable to that of all-trans retinoic acid.
Article
The oxymercuriation-demercuriation (OM–DM) of methyl (E)-communate with mercury(II) acetate yielded mainly the hydration product of the 14,15-double bond. The isopimarane oxide methyl (8R,12R)-epoxyisopimar-15-en-19-oate, the endoperoxide methyl (8S,12R,13S)-13,17-epidioxy-8,12-epoxylabd-14-en-19-oate and the diorganomercurial bis-(4β-methoxycarbon...
Article
A simple approach to A-ring-gamma-dioxygenated terpenoids is described which involves two key steps, namely, selenium-catalyzed selective allylic chlorination of polyprenoids and titanocene-mediated radical cyclization of epoxypolyprenes. We have applied this synthetic route to the first synthesis of the diterpene, (13E)-ent-labda-8(17),13-diene-3...
Article
Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy- or hydroxy-Ti(III) complexes considerably decreases the energy of activation for C-O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent's reagent in organic...