Microbial Transformation of (+)-and (-)-Dehydrogriseofulvin by Streptomyces Species Analyzed by ²H Nuclear Magnetic Resonance Spectroscopy

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To elueidate the stereochemical course of the microbial transformation of (+)-dehydrogriseofulvin (DGF) by Streptomyces species, (+)-[5'-²H] DGF, which was obtained by dehydrogenation of (+)-[5'α, 5'β-²H] epigriseofulvin, was incubated with S. cinereo-crocatus. The structure of the product was identified as (+)-[5'α-²H] griseofulvin (GF) by ²H nuclear magnetic resonance spectroscopy. The results of incubations of (-)-and (+)-DGF with eight Streptomyces species (S. cinereocrocatus, S. roseochromogenus, S. bikiniensis, S. griseinus, S. durhamensis, S. californicus, S. fimbriatus, and S. cinereoruber) showed that (-)-and (+)-DGF were isomerized to each other and converted to (+)-GF as the main product, although some (-)-GF was also formed depending on the microorganisms used. In particular, incubation of (+)-DGF with S. cinereoruber yielded (-)-GF as the main product. In addition, (±)-DGF was transformed by S. cinereocrocatus to the naturally occurring (+)-GF in 48% yield. The enantiomer ratios of DGF and GF obtained by microbial transformation were calculated from the [α]_D values of corresponding enantiomer mixtures.