Sulfur-containing beta-amino alcohols as catalysts in enantioselective synthesis

Oxazaborolidine catalysts generated in situ from cyclic or acyclic sulfur containing (R)-cysteine, (S)-penicillamine and (S)-methionine derivates and BH3 have been applied successfully to the enantiocontrolled, catalytic reduction of aromatic ketones. The corresponding sec alcohols could be obtained in excellent enantiomeric excess, up to 100% ee. Using these chiral auxiliaries in the enantioselective addition of diethylzinc to aldehydes afforded optically active sec alcohols in enantiomeric excess up to 93% ee. (C) 1997 Elsevier Science Ltd.