Efficient and practical asymmetric synthesis of 1-tert-butyl 3-methyl (3R,4R)-4-(2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)piperidine-1,3-dicarboxylate, a useful intermediate for the synthesis of nociceptin antagonists
作者:Hideki Jona、Jun Shibata、Masanori Asai、Yasuhiro Goto、Sachie Arai、Shigeru Nakajima、Osamu Okamoto、Hiroshi Kawamoto、Yoshikazu Iwasawa
DOI:10.1016/j.tetasy.2009.07.046
日期:2009.11
An efficient and practical asymmetric synthesis of 1-tert-butyl 3-methyl (3R,4R)-4-(2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)piperidine-1,3-dicarboxylate 1, a useful intermediate for the synthesis of nociceptin antagonists, has been developed. This method includes the following key steps: (1) diastereoseiective reduction of a chiral enaminoester 3 having (R)-1-phenylethylamine as a chiral pool constituent with the use of a combined TFA-NaBH4 reduction system and (2) efficient isomerization from 3,4-cis-substituted piperidine 8 to 3,4-trans-substituted piperidine 1 under basic conditions. The above methods proved to be applicable for large-scale operation and hundred grams of enantiomerically pure compound 1 (>98% ee) was obtained. (C) 2009 Published by Elsevier Ltd.