DECISIVE EFFECTS OF C-N AXIAL CHIRALITY OF INTERMEDIARY ENOLATES ON THE STEREOCHEMICAL COURSE OF p-LACTAM FORMATION FROM β-BRANCHED α-AMINO ACID DERIVATIVES VIA MEMORY OF CHIRALITY

摘要

Stereochemistry of P-lactam formation of P-branched a-amino acid derivatives via a MOC strategy was investigated.The 4-exo-trig cyclization of axially chiral enolates generated from L-threonine and L-allo-threonine derivatives proceeded predominately with inversion of the configuration at the newly formed tetrasubstituted carbon,irrespective of the chirality at the p-carbon of the P-lactam precursors.These results indicated that C-N axial chirality of the intermediary enolates generated from the a-amino acid derivatives has decisive effects on the stereochemical course of P-lactam formation even in the presence of an sp~3-chiral center at the p-carbon.