48(P-5) 生体触媒による不斉反応 : 不斉水素化に関与する酵素系(ポスター発表の部)

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Optically active α-substituted ketone derivatives are widely employed as chiral synthons in asymmetric syntheses and there is continuing interest in the development of efficient procedures to prepare them in enantiopure form. Biocatalysts such as enzymes are now widely utilized in the organic synthesis, as stereoselective reaction is expected in an enzymatic reaction. Three reductases (Reductase I, II and III) participating in the asymmetric reduction of enones to give α-chiral ketones were isolated from the cultured cells of Nicotiana tabacum. Reduction of endocyclic C=C double bond of s-trans enones by the Reductase I afforded highly optically active ketones with R configuration, whereas reduction by the Reductase III geve ketones with S configuration. On the other hand, reduction of exocyclic C=C double bond of s-cis enones by the Reductase II gave optically active ketones with S configuration. In addition, reductases (Reductase IV and V) from A. longa and Reductase VI from E. gracilis reduced s-trans enones to afford (R)-ketones. Two esterases (Esterase I and II) participating in the enantioselective hydrolysis of enol esters to give α-chiral ketones were isolated from the cultured cells of Marchantia polymorpha. The enantioselectivity was opposite between these two esterases and both of them reversed the stereoselectivity of protonation of the enol intermediate when the chain length of alkyl substituents at α-position of ketone was increased. Thus, two examples have been demonstrated showing that the utilization of enone reductase and esterase is efficient to prepare highly optical active ketones via asymmetric hydrogenation in an aqueous medium.
天然有機化合物討論会の論文
2001-09-01

48(P-5) 生体触媒による不斉反応 : 不斉水素化に関与する酵素系(ポスター発表の部)

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