Preparation of all stereoisomers of 2-allyl-2-methyl-3-hydroxycyclopentanone by desymmetric processes based on a microbial oxidation and reduction system

All stereoisomers of 2-allyl-3-hydroxy-2-methylcyclopentanones 2–5 were prepared in high conversion and in an optically pure form by microbial reduction and oxidation. The reduction of symmetric diketone 1 by Geotrichum candidum NBRC 4597 under anaerobic conditions gave 2 in 83% yield (98% conversion), >99% de, and >99% ee, whereas the reduction of 1 by G. candidum NBRC 5767 under aerobic conditions gave 3 in 75% yield (99% conversion), >99% de, and >99% ee. Oxidation of meso-diol 6 by G. candidum NBRC 5767 under aerobic conditions afforded 4 in 83% yield (99% conversion) and >99% ee, while oxidation of meso-diol 7 by Mucor heimalis IAM 6095 in the presence of cyclohexanone as a co-oxidant afforded 5 in 68% yield (75% conversion) and >99% ee.