Asymmetric synthesis of cis-4- and trans-3-hydroxypipecolic acids

摘要

Enantioselective syntheses of cis-4- and trans-3-hydroxypipecolic acids from 2,3-epoxy-5-hexen-1-ol (7) are described, Regioselective C-3 or C-2 ring opening of the epoxide by the appropriate nitrogen nucleophile is the key step in each route. As enantiomeric ally enriched epoxy alcohols are readily available in any configuration by Sharpless epoxidation, both enantiomers are equally accessible. This approach was also employed to synthesize the natural product baikiain and the important synthetic intermediate trans-3-hydroxy-2-bydroxymethylpiperidine.