Synthesis of all stereoisomers of cognac lactones via microbial reduction and enzymatic resolution strategies

Both enantiomers of the diastereomeric cognac lactones have been synthesise d using enzyme assisted reactions in the enantiodifferentiating step. This was accomplished by baker's yeast reduction of their precursors 3-methyl-4- oxononanoic acid and ester and by enzymatic hydrolysis of the latter. An in hibition of hydrolases by the products was observed. Trans-(+)-, trans-(-)- , cis-(+)- and cis-(-)-cognac lactones having 99, 88, 88 and 99% e.e., resp ectively, were thus obtained. Their CD spectra have also been studied. (C) 2001 Elsevier Science Ltd. All rights reserved.