Carbon skeleton of polysubstituted pyroglutamates with three contiguous asymmetric centers was built up in one base-induced coupling/cyclization reaction of α-sulfonylacetamide with 2-bromo-2-propenoates. A simple transformation to 3-substituted prolinols can be easily achieved via reduction and desulfonation. A ring expansion of prolinol has been used as the key step in the formal synthesis of isoguvacine and paroxetine. The one-pot conversion of 3-substituted prolinol to the 3-substituted pyroglutamic acid is also reported.
A facile synthesis of 3-aryl pyroglutamic acids via stepwise [3+2] annulation and desulfonated hydrolysis is reported. Base-induced coupling/cyclization reactions of alpha-sulfonylacetamide with various beta-functional groups of (Z)-2-bromoacrylates yielded three contiguous chiral centers on the polysubstituted pyroglutamates system with trans-trans orientation in a one-pot synthesis. This facile strategy was used to synthesize amino acid derivatives baclofen and chlorpheg. (C) 2003 Published by Elsevier Science Ltd.