A series of yeasts were used in the bioreductions of aliphatic and aromatic gamma- and delta -ketoacids and esters to investigate the preparation of enantiomerically pure gamma- and delta -lactones through the intermediacy of their corresponding gamma- and delta -hydroxyacids and esters. Bioreduction of ethyl 4-oxononanoate 2a with Pichia etchellsii afforded the gamma -nonanolide (+)-5a with 99% e.e., while Pichia minuta proved to be the best choice for the bioreduction of ethyl 2-oxocyclohexylacetate 2e, which afforded cis-(-)-5e and trans-(-)-5e with 98 and 99% e.e., respectively. Reduction of 3-(2-oxocyclohexyl)propionic acid 3e with Pichia glucozyma gave predominantly the corresponding delta -lactone trans-(-)-6e with 94% e.e., whose absolute configuration was determined by means of CD spectroscopy.
