85 Streptomyces cinereocrocatusの無細胞系による(-)-Dehydrogriseofulvinの(+)-Griseofulvinへの還元の立体化学 : NADPHの水素の立体特異的取り込み

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To elucidate the stereochemistry of the hydrogenation of (-)-dehydrogriseofulvin (1a) to (+)-griseofulvin (2a) by Streptomyces cinereocrocatus, we have prepared from the microorganism a cell-free system and its partially purified system which can transform 1a to 2a. An assumption that NADPH might be a cofactor in the hydrogenation of 1a to 2a was confirmed by the experiments which showed increment of the transformation ratio by NADPH added in an incubation mixture of the cell-free system. The stereochemistry of hydrogenation was demonstrated by analysis of the products (2d-e) which were obtained by the conversion of (-)-[5'-^2H]-dehydrogriseofulvin (1b)- and also by the conversion of 1a in a medium containting deuterium oxide. Further, the stereochemistry of the products (2a,g) of NADPH-dependent hydrogenation was investigated by the conversion of 1a under the conditions which contained (4R)-[4-^2H]- or (4S)-[4-^2H]-NADPH in a partially purified enzyme system. The results unequivocally indicated that the 5'α- and 5'β-hydrogens of (+)-griseofulvin originate from 5'-hydrogen of (-)-dehydrogriseofulvin and a proton from the medium, respectively, and that the origin of 6'α-hydrogen is a hydride ion donated by pro-4R-hydrogen of NADPH, as investigated by 270 MHz ^1H-NMR.
天然有機化合物討論会の論文
1985-09-07