TiCl < inf > 4 < /inf > promoted menthyl ester chiral auxiliary mediated synthesis of chiral syn-β-amino esters and applications of a representative syn-β-amino ester

Abstract

β-Amino esters were obtained in up to 78% yield with 72:28-96:4 diastereomeric ratios by the reaction of the chiral titanium enolate of menthyl esters, prepared using the TiCl4/Et3N reagent system with prochiral imines. A representative syn-β-amino ester derivative has been used for the resolution of racemic mandelic acid to obtain a sample with > 99% ee in a single step. A representative syn-β-amino ester was converted to the corresponding N-deprotected amino ester using the Pd-C/HCOOH reagent system, and then to the corresponding β-amino acid using the glacial CH3COOH/HCl reagent system, and to the corresponding β-lactam derivative with partial epimerization by the reaction using C2H5MgBr. © 2010 Elsevier Ltd. All rights reserved.