Diastereoselective synthesis of 3,5-trans-(+)-(3R,5R)-3-carbomethoxycarbapenam from 3-hydroxypyridine: questioning the stereochemical assignment of the natural product

An enantio- and diastereoselective synthesis of the methyl ester of 3,5-trans-(3R,5R)-carbapenam-3-carboxylic acid from 3-hydroxypyridine via (2R,5S)-trans-5-acetoxy-2-allylpiperidine has been achieved by employing the piperidine–pyrrolidine ring-contraction reaction as the key step. The synthesis indicates that the configuration of the naturally occurring 3,5-trans-carbapenam-3-carboxylic acid is not the revised (3S,5S), but rather the originally assigned (3R,5R) configuration.