P. Chinna Chenchaiah

Removal of O- and N-benzyl groups by fungal biotransformation

Abstract Biotransformation by resting cultures of the aerobic fungi Mortierella isabellina NRRL 1757 and Helminthosporium species NRRL 4761 can be used as method for the removal of O- and N-benzyl groups, respectively, under neutral, room temperature conditions.

Fungal hydroxylation of ethyl benzene and derivatives

Abstract The fungus Mortierella isabellina converts ethyl benzene and a number of parasubstituted derivatives to the corresponding optically active 1-phenylethanols with enantiomeric excesses between 5 and 40%. Hydrogen removal from the substrate preceeds product formation and is stereochemically independent of it.

Synthesis of chiral molecules from non-chiral crystals by controlled reaction at a single surface

A procedure is described for performing reactions at a single face of a single crystal of organic compounds, using as examples the cis-dihydroxylation of tiglic and crotonic acids by osmium tetraoxide, and the dibromination of tiglic acid. For molecules whose orientation in the crystalline state is appropriate, reactions carried out in this way can produce enantiomerically enriched products from a non-chiral crystal and reagent. Enantiomeric excesses are dependent upon the crystal quality; values up to 30% have been achieved in the reactions of tiglic acid with osmium tetraoxide or bromine vapour.

A new approach to the synthesis of chiral molecules from nonchiral reactants. Asymmetric induction by reaction at one surface of a single (nonchiral) crystal

Reaction at one surface of a single achiral crystal can produce chiral products having optical purities approaching 100%.

Syntheses of 2α- and 2β-deuterio-testosterones and -androst-4-ene-3,17-diones

Testosterone and androst-4-ene-3,17-dione with a deuterium label in the 2α- or 2β-position have been synthesized from a common intermediate, 5α-androst-2-ene-5α,17β-diol. An improved preparation of the latter is described, together with its conversion via epoxidation, reductive epoxide opening, and subsequent oxidation and dehydration to 2β-labelled Δ4-3-oxo steroids. Treatment of the same precursor with labelled diborane leads, by a similar synthetic sequence, to both 2α- and 2β-labelled Δ4-3-oxo steroids. The stereochemical integrity of the products has been determined by high-field deuterium n.m.r.