RESUMO
The fermentation of 10-deacetylbaccatine III (10-DAB) (1) with Curvularia lunata afforded 4-deacylwallifoliol (4) and wallifoliol (5), the only natural taxoid with the unusual 5/6/6/6/4 ring system. The X-ray structure of compound 4 is reported. The skeletal rearrangements induced by the microbial enzymatic systems are also discussed.
Assuntos
Ascomicetos/química , Taxoides/química , Taxoides/isolamento & purificação , Biotransformação , Ensaios de Seleção de Medicamentos Antitumorais , Modelos Moleculares , Estrutura Molecular , Ressonância Magnética Nuclear BiomolecularRESUMO
The fermentation of 10-deacetylbaccatin III (10-DAB) (1) with Curvularia lunata afforded the taxane hemiacetals 2a and 3, characterized by extensive structural modification, including C-2 to C-1 transbenzoylation, oxidation of the C-2 hydroxyl, formation of a C-9/C13 hemiacetal, epimerization at C-10, and migration of the endocyclic double bond to an exocyclic location. In compound 3, an acetate-assisted opening of the oxetane ring was also observed.
Assuntos
Ascomicetos/metabolismo , Hidrocarbonetos Aromáticos com Pontes/química , Éteres Cíclicos/química , Taxoides/química , Biotransformação , Estrutura Molecular , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
A new dimeric fungal metabolite, racemic acremine G, was isolated from cultures of the fungus Acremonium byssoides A20, along with the known acremines A-F. Its structure was elucidated by NMR spectroscopy and X-ray crystallography. A possible biosynthetic pathway is discussed. Acremine G mildly inhibited the growth of sporangia of Plasmopara viticola.
Assuntos
Acremonium/química , Benzoquinonas/química , Benzoquinonas/isolamento & purificação , Cristalografia por Raios X , Itália , Conformação Molecular , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , EstereoisomerismoRESUMO
1-O-Acyl-sn-glycero-3-phosphocholine and 1-O-acyl-sn-glycero-3-phosphoric acid have been prepared selectively and with high yields from the corresponding diols, glycerophosphoryl choline and glycerol-3-phosphate. Starting from the diols, the activated tin ketals were prepared in 2-propanol by reaction with dialkyltin oxide. The intermediates were acylated in the same solvent with long-chain fatty acid chlorides, giving the corresponding 1-acyl-lyso-phospholipids in high yield and with complete regioselectivity. The catalytic nature of the tin-mediated acylation and the relevance of the solvent are discussed.
RESUMO
Investigation of the extracts of a culture of Cladosporium tenuissimum, a known hyperparasite of several rust fungi, gave rise to the isolation of cladosporols B-E (2-5). Their structure and stereochemistry were elucidated on the basis of 1H and 13C NMR evidence and CD measures. Cladosporols 1-5 were active in inhibiting the urediniospore germination of the bean rust agent Uromyces appendiculatus.
Assuntos
Cladosporium/química , Cromatografia em Gel , Cromatografia em Camada Fina , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Estrutura Molecular , Extratos Vegetais/química , Esporos Fúngicos/fisiologiaRESUMO
Investigations carried out on secondary metabolites produced in culture by a hypovirulent strain of Cryphonectria parasitica allowed the isolation of several compounds which were characterized by NMR analysis and derivatization reactions. The most abundant metabolite was a new compound, called cryphonectric acid (1). Other metabolites were diaporthin, the only known phytotoxic compound isolated from both virulent and hypovirulent strains of C. parasitica, (+)-orthosporin, and L-p-hydroxyphenyllactic acid (HOPLA). Root growth activity of the purified compounds was evaluated both on tomato seedlings and maize subapical segments.
Assuntos
Ascomicetos/química , Benzofuranos/isolamento & purificação , Benzofuranos/química , Benzofuranos/farmacologia , Cromatografia Líquida de Alta Pressão , Concentração Inibidora 50 , Solanum lycopersicum/efeitos dos fármacos , Solanum lycopersicum/crescimento & desenvolvimento , Espectrometria de Massas , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Fenilpropionatos/química , Fenilpropionatos/isolamento & purificação , Fenilpropionatos/farmacologia , Desenvolvimento Vegetal , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Plantas/efeitos dos fármacos , Pironas/química , Pironas/isolamento & purificação , Pironas/farmacologia , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , Estereoisomerismo , Zea mays/efeitos dos fármacos , Zea mays/crescimento & desenvolvimentoRESUMO
Alkyl-substituted olefins are epoxidized by perfluoro-cis-2,3-dialkyloxaziridines under particularly mild conditions. Electron deficient substrates (e.g. alpha,beta-enones) can also be epoxidized, and the more electron poor the double bond is, the more severe the reactions conditions become. The epoxidation is chemoselective (secondary alcohols and their ethers do not interfere), site selective (the monoepoxide of a diene can be obtained), and stereoselective (cis-alkenes afford cis-epoxides). Various complex and polyfunctional substrates of natural origin (monoterpenes, sesquiterpenes, steroids) have been transformed effectively.