APPLICATION OF THE BLAISE REACTION - STEREOSELECTIVE SYNTHESIS OF (4R)-TERT-BUTYL 3-AMINO-4-TRIMETHYLSILYLOXY-2-ALKENOATES FROM (R)-CYANOHYDRINS

O-Trimethylsilyl protected (R)-cyanohydrins 3 react with Reformatsky r eagents from tert-butyl 2-bromoesters 4 and zinc dust (Blaise reaction ) to give the corresponding addition products in high yields. Workup w ith an aqueous solution of NH4Cl at low temperature gives (4R)-tert-bu tyl 3-amino-4-trimethylsilyloxy-2-alkenoates (R)-5 without racemizatio n. Hydrogenation of the alkenoates 5 to the corresponding tert-butyl b eta-amino-gamma-hydroxyalkanoates 6, resulting in a mixture of two dia stereoisomers, was only possible under special hydrogenation condition s. With HCl in dichloromethane compounds 6 cyclize to the correspondin g beta-amino-gamma-hydroxybutyrolactones 8. (C) 1998 Elsevier Science Ltd. All rights reserved.