Evaluation of the Efficiency of the Chiral Quaternary Ammonium Salt β-Np-NAS-Br in the Organic-Aqueous Phase-Transfer Alkylation of a Protected Glycine Derivative
allylation of glycine tert-butyl ester benzophenone Schiff base (1). This revealed the practical conditions for the asymmetric synthesis of both natural and unnatural α-amino acids, whose usefulness was demonstrated by the formal enantioselective synthesis of antibioticL-azatyrosine.
Highly enantioselective monoalkylation of p-chlorobenzaldehyde imine of glycine tert-butyl ester under mild phase-transfer conditions
作者:Takashi Ooi、Yuichiro Arimura、Yukihiro Hiraiwa、Lin Ming Yuan、Taichi Kano、Toru Inoue、Jun Matsumoto、Keiji Maruoka
DOI:10.1016/j.tetasy.2006.01.019
日期:2006.2
The selective monoalkylation of glycine tert-butyl ester aldimine Schiff base 3 has been realized in high chemical yield with excellent enantioselectivity under mild liquid-liquid phase-transfer conditions by the use of binaphthyl-derived chiral quaternary ammonium bromides 7 and 8 as catalysts. This achievement demonstrates that 3 can be used as a cost-effective substrate for the preparation of optically active alpha-alkyl-alpha-amino, acid derivatives by chiral phase-transfer catalysis. (c) 2006 Elsevier Ltd. All rights reserved.
Enantioselective Syntheses of Aeruginosin 298-A and Its Analogues Using a Catalytic Asymmetric Phase-Transfer Reaction and Epoxidation
We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic