Pyrrolidinones derived from (S)-pyroglutamic acid. Part 1. Conformationally constrained glutamate

Novel conformationally constrained pyroglutaminols and pyroglutamates are r eadily available using an alpha,beta-unsaturated bicyclic lactam as a templ ate for diastereocontrolled enolate additions in the key step; zinc enolate s are particularly effective in this regard. The bicyclic ring system both controls and permits the determination of ring stereochemistry. The utility of this methodology is demonstrated by a formal total synthesis of the NMD A receptor agonist, CPAA 11.