BAKERS-YEAST REDUCTION OF PROCHIRAL GAMMA-NITROKETONES - ENANTIOSELECTIVE SYNTHESIS OF (S)4-NITROALCOHOLS

The baker's yeast reduction of seven different prochiral nitroketones 1a-g occurred on the re face of the carbonyl group, thus affording the (S)-nitroalcohols 2a-g, with different level of enantioselectivity (e.e. 15-99%). The best results (e.e. = 99%) were achieved when the substituent R is markedly different from the nitroalkyl group [e.g. 1a (R = Me) and le (R = o-MeO-C6H4)]. The e.e. and the configuration of the bioproducts were assigned by NMR study of the corresponding Mosher esters and in one case (2d) by means of chemical correlation. The syntheses of optically active lactone 7 and pyrrolidine 11 starting from 2d are also described.