Stereoselective syntheses of substituted tert-butyl 3-allyl-4-hydroxypiperidine-1-carboxylate

tert -Butyl 3-allyl-4-oxopiperidine-1-carboxylate and its derivatives substituted at the 3-position and in the allylic fragment reacted with L-selectride in anhydrous tetrahydrofuran to give tert -butyl (3 R ,4 S )-3-allyl-4-hydroxypiperidine-1-carboxylates ( cis isomers) in quantitative yield. The Mitsunobu reaction of the latter with formic or benzoic acid, followed by alkaline hydrolysis, afforded the corresponding trans (3 R ,4 R ) isomers.