The stereoselective synthesis of penmacric acid, an optically active C-4 substituted pyroglutamicacid, has been efficiently achieved through an unusual 11-step sequence starting from simple N-triisopropylsilylpyrrole. The key-steps are the initial addition of the pyrrole nucleus onto a chiral nitrone and the obtention of the pyroglutamicacid moiety by reductive hydrogenation of the pyrrole followed
The total syntheses of penmacric acid and its three stereoisomers were accomplished through the intermolecular radical addition reaction of the 4-pyrrolidyl radical derived from trans-4-hydroxy-L-proline. Furthermore, 1',3-diepi-penmacric acid was synthesized stereoselectively via double stereoinduction in the radical reaction. (C) 2013 Elsevier Ltd. All rights reserved.