PREPARATION OF OPTICALLY ACTIVE GAMMA- AND DELTA-LACTONES BY MICROBIOLOGICAL REDUCTION OF THE CORRESPONDING KETO ACIDS.

It was found, by means of simple screening methods, that several yeasts (Saccharomyces and Candida), molds (Cladosporium), and bacteria (Sarcina) are able to reduce keto acids to hydroxy acids, which are easily converted into lactones. Chemical analysis showed that some of the microorganisms (Saccharomyces and Candida) produce dextrorotatory lactones and others (Cladosporium and Sarcina) produce levorotatory lactones. High yields of dextrorotatory (both gamma- and delta-lactones) were obtained by using Saccharomyces cerevisiae. The physical properties of the carefully distilled lactones obtained indicated high purity and high optical purity.