A general entry to 2-(2-hydroxyalkyl)piperidines via iterative asymmetric dihydroxylation to cause enantiomeric enhancement

Both enantiomers of 2-(2-propenyl)piperidine (1) (76-88% ee), prepared via the first AD of 5-hexenyl azide, underwent the second AD to provide all of the four stereoisomeric 2-(2-hydroxypropyl)-piperidines (2) with enantiomeric enhancement (>98% ee). An asymmetric synthesis, starting from 2,of several 2-(2-hydroxyalkyl)piperidine alkaloids are demonstrated. (C) 1997 Elsevier Science Ltd.