Anjana Sinha-Bagchi

A general approach to γ-lactones via osmium-catalyzed asymmetric dihydroxylation. Synthesis of (−)- and (+)-muricatacin.

Abstract Both enantiomers of hydroxy γ-lactones have been prepared highly enantioselectively (92–99% ee) using either AD-mix-β or AD-mix-α with both β,γ- and γ,δ-unsaturated esters. The method is exemplified by the three-step synthesis of (−) and (+)-muricatacin in 74% yield and >99% ee.

Synthesis of All Four Isomers of Disparlure Using Osmium-Catalyzed Asymmetric Dihydroxylation.

Disparlure, the sex attractant emitted by the female gypsy moth, Porthetiu dispar (L.), and its (-)-enantiomer were synthesized in 43% yield and >99% ee, starting from undecanal and using the asymmetric dihydroxylation (AD) reaction. Similarly, the,two trans- isomers of disparlum were synthesized in 51% yield and 95% ee.

Thermostable enzymes in organic synthesis, Part 6. Total synthesis of (S)–(–)-zearalenone using a TBADH-generated trifunctional chiron

Chiral alcohols produced by Thermoanaerobium brockii alcohol dehydrogenase (TBADH)-catalysed asymmetric reduction of polyfunctional ketones are useful building blocks for natural products synthesis. In particular, the ability of TBADH to discriminate between two ketones having equal chemical reactivity is demonstrated by enzymatic reduction of dec-9-ene-2, 6-dione to produce optically pure (S)-2-hydroxydec-9-en-6-one. The total synthesis of (S)-(–)-zearalenone with optical purity that exceeds 99.5% has been achieved by using the latter compound as a starting material.

Modular approach to annonaceous acetogenins. total synthesis of asimicin and bullatacin.

Abstract Starting with a variety of non-functionalized carbon skeletons and employing various combinations of five key transformations provides an easy access to most of the naturally occurring Annonaceous acetogenins. A particular emphasis is given to the dominant structural feature that appears in more than 40% of the known acetogenins. This is a linear, ten-carbon skeleton comprising two adjacent tetrahydrofurane rings flanked with two hydroxyl groups. Efficient, flexible syntheses of asimicin and bullatacin demonstrate this approach.

Withanolides of Datura metel

Abstract The leaves of Datura metel yielded three new withanolides in addition to lycium substance B, previously reported from other Datura species. The structures of the withanolides, clarified by comprehensive spectral analysis, showed features of typical daturalactones as well as of the withanolides of D. metel. p -Hydroxy cinnamic acid amide of tyramine was also isolated.

A practical approach to enantiomerically pure cis-epoxides. synthesis of (+)-disparlure

Abstract An efficient synthesis of (+)-disparlure has been achieved in >99.8% ee via the Sharpless asymmetric dihydroxylation followed by Mitsunobu inversion of one hydroxyl group and conversion of the resultant erythro diol to the cis epoxide.

Withanolides from Datura tatula

Abstract Withatatulin, a new 21-hydroxy withanolide and several other known withanolides have been isolated from the leaves of Datura tatula . The structure of the new compound has been elucidated from comprehensive spectral analysis and by establishing its chemical relationship with a withanolide of known structure. Physalindicanol A, a C 28 -sterol has also been isolated from this source.

Withanolides of Datura fastuosa leaves

Abstract The leaves of Datura fastuosa yielded two new withanolides, withafastuosins A and B, in addition to withametelin, previously reported from D. metel . The structures of the withanolides were established on the basis of detailed spectral and chemical evidence.