Synthesis of new bicyclic analogues of glutamic acid

Regioisomeric 3-hydroxyisoxazolinyl prolines {[HIP-A (+/-)-6 and HIP-B
(+/-)-7], which represent a restricted conformation of NMDA, AMPA, and
kainic acid, potent and selective agonists at ionotropic glutamate
receptors, have been prepared through two different strategies. In the
first approach bromonitrile oxide was added to N-BOC-Delta(3)-pyrroline
or N-BOC-Delta(3)-pyrrolin-2-one and the carboxylic group was
subsequently appended. The alternative strategy is based on the
cycloaddition of the same 1,3-dipole to NBOC-3,3-didehydroproline methyl
ester, (C) 1999 Elsevier Science Ltd. All rights reserved.}