DIASTEREOSELECTIVE AND ENANTIOSELECTIVE REDUCTION OF BETA-KETO-ESTERS DERIVED FROM CYCLOPENTANONE, CYCLOHEXANONE, PIPERIDONE AND TETRALONE BY NON-FERMENTING BAKER YEAST

Under ''non-fermenting'' conditions, i.e. in tap water, in the absence of nutrients, baker''s yeast (25-380 g/g of substrate, aerobic) reduces .beta.-keto esters such as those mentioned in the title with better selectivity than under the normally employed ''fermenting'' conditions (sugar and nutrients, CO2 development). With the .beta.-keto esters containing the tetralone substructure, large amounts of yeast are required (250-380 g/g); the substrate disappears in the biomass, and the desired reduction product can be extracted after reaction times of up to a week at 30.degree.. The configurations of most products (16-24) is established. Generally, the (R)-.beta.-keto ester is reduced faster than the (S)-enantiomer (the two esters are in equilibrium under the reaction conditions), and the hydride transfer takes place preferentially from the diasterotopic Re-face. The .beta.-hydroxy esters thus available are useful starting materials for syntheses of enantiomerically pure compounds (EPC).