that, after optimization of the ring-enlargement reaction conditions, could be efficiently transformed into the corresponding 3-hydroxypiperidines. This approach was applied to the asymmetric synthesis of (+)-isofagomine relying on regio- and stereoselective oxirane opening with the cyanide anion of a pivotal epoxypyrrolidine. iminosugar - piperidine - ringenlargement - epoxide opening