Chemo- and Regioselective Syntheses of Enantiopure Aminopyrrolidinones as Building Blocks for Constrained Peptidomimetics

Starting from natural asparagine the synthesis of the N-protected enantiomerically pure 3-and 4-aminopyrrolidinones (1) and (3) was accomplished.The incorporation of these building blocks into conformationally constrained peptidomimetics was demonstrated by the synthesis of the potential dopamine receptor modulator (14b) (B-PAOPA).Furthermore, Freidinger y-lactams including the protected dipeptide mimetics @a-c) and (9) were prepared.The optical integrity of the synthesis was established by NMR analysis of the ureas (10a,b).Confornationally constrained peptide analogs represent an important family of compounds employc :d for the development of enzyme inhibitors and receptor ligands.'Additionally,interesting insights into the biologically