Enzymes in organic synthesis-29 : Preparations of enantiomerically pure cis -2,3- and 2,4-dimethyl lactones via horse liver alcohol dehydrogenase-catalyzed oxidations

Further examples of the broad applicability of horse liver alcohol dehydrogenase-catalyzed oxidations of meso-diols as a route to chiral lactones of asymmetric synthetic value are described. The acyclic meso substrates, cis-2,3-dimethyl- and -diethylbutane-l,4-diols, and cis-2,4-dimethylpentane-l,5diol, are stereospecifically oxidized in good yields to the corresponding enantiomerically pure γ- and δ-lactones. The oxidation of cis-3,4-bis(hydroxymethyl)thiacyclopentane is similarly stereospecific. For each meso-diol the oxidation takes place with a net stereospecificity for the hydroxymethyl groups attached to the S-enters, with the initially formed hydroxyaldehydes undergoing further enzymecatalyzed oxidations via their hemiacetal forms to produce lactone products directly.