Asymmetric trans-dihydroxylation of cyclic olefins by enzymatic or chemo-enzymatic sequential epoxidation and hydrolysis in one-pot

摘要

Novel and efficient one-pot enzymatic and chemo-enzymatic synthetic methods are developed for the asymmetric trans-dihydroxylations of cyclic olefins la and lb via sequential epoxidation and hydrolysis. The Novozym 435~R-mediated epoxidation of cyclohexene la and subsequent hydrolysis of the intermediate cyclohexene oxide 2a with resting cells of Sphingomonas sp. HXN-200 in one-pot gave (1R,2R)-cyclohexane diol 3a in 84% ee and 95% conversion. trans-Dihydroxylation of N-benzyloxycarbonyl 3-pyrroline lb with the same enzymatic system gave the corresponding (3R,4R)-N-benzyloxycarbonyl-3,4-dihydroxy-pyrrolidine 3b in 93%> ee and 94% conversion. In the one-pot chemo-enzymatic system, epoxidation of N-benzyloxycarbonyl 3-pyrroline 1b by m-CPBA and subsequent hydrolysis of epoxide intermediate 2b with resting cells of Sphingomonas sp. HXN-200 gave the trans-diol (3R,4R)-3b in 92% ee and 94-97% conversion. While the trans-dihydroxylation of cyclohexene la to (1R,2R)-cyclohexane diol 3a is reported for the first time, the trans-dihydroxylation of N-benzyloxycarbonyl 3-pyrroline lb to (3R,4R)-3b with such an enzymatic or chemo-enzymatic system afforded a much higher product concentration than the same reaction with the system using a microorganism containing the two necessary enzymes. The developed one-pot enzymatic and chemo-enzymatic systems for the asymmetric trans-dihydroxylation of olefins are new, easy to prepare, adjust and operate, are high yielding, complementary to Sharpless asymmetric dihydroxylation and particularly useful for the asymmetric synthesis of cyclic trans-diols.