Bioreduction with immobilized bakers' yeast proceeded smoothly in hexane by using alcohols, such as methanol, ethanol, and propan-2-01, instead of glucose, as an energy source; ethyl 3-oxobutanoate and ethyl benzoylformate were each reduced to the corresponding chiral hydroxy esters with a high enantiomeric purity.

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(5Z,13S)-5-Tetradecen-13-olide, a synergist of the aggregation pheromone of the flat grain beetle, was synthesized in an optically pure form by means of an asymmetric bioreduction of the intermediate acetylenic keto acid with immobilized bakers’ yeast entrapped in gels of calcium alginate.

Immobilized baker's yeast entrapped in calcium alginate beads, ca 1.5 mm diameter, was used more than 10 times in water and reduced ethyl 3-oxobutanoate and ethyl benzoylformate to the corresponding chiral hydroxy esters in good chemical yields and in high enantioselectivities. The biocatalyst was also successfully used in organic/water solvent systems such as hexane/water and acetonitrile/water, and in other systems, particularly in hexane, converted keto esters into their individual chiral hydroxy esters.