Pyruvate decarboxylase catalysed formation of terpenoid α-hydroxy ketones

Enzyme extracts of the wild type yeast Zygosaccharomyces bisporus were applied for the pyruvate decarboxylase catalysed condensation of pyruvate and (R)-(+)- and (S)-(-)-perillyl aldehyde, (±)-citronellal, neral, geranial or (R)-(-)-myrtenal to form novel α-hydroxy ketones. Best yields were obtained when the transformation medium contained 25% (v/v) of the cosolvent N,N-dimethylformamide. Conversion of (R)-(+)-perillyl aldehyde to (1R)-1-hydroxy-1-[(4′R)-4′-isopropenyl-1-cyclohexen-1-yl]-2-propanon e proceeded highly stereospecifically (> 99% de), whereas the stereoselectivity was somewhat less in the transformation of (S)-(-)-perillyl aldehyde (58% de) and (R)-(-)-myrtenal (92% de). All of the new compounds imparted characteristic odour impressions as determined by means of GC-olfactometry.