The differential oxidation of five and six-membered endocyclic enecarbamates was investigated employing m-CPBA, DMD, as well as enantioselective protocols such as the Kochi-Jacobsen-Katsuki's epoxidation and the Sharpless dihydroxylation. By this strategy the syntheses of beta-hydroxyprolines and beta-hydroxypipecolic acids were accomplished. X-Ray crystallographic analysis of the trans-beta-hydroxypipecolic acid was instrumental to solve structural assignment conflicts. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.392134133416