A New General Approach to Enantiomerically Pure Cyclic and Open-Chain (<i>R</i>)- and (<i>S</i>)-α,α-Disubstituted α-Amino Acids
作者:Daniel Obrecht、Clive Spiegler、Peter Schönholzer、Klaus Müller、Heinz Heimgartner、Friedrich Stierli
DOI:10.1002/hlca.19920750522
日期:1992.8.13
racemic N-acylated α,α-disubstituted amino acids were resolved by coupling to chiral amines 15-18 derived from (S)-phenylalanine to form diastereoisomers 19/20 or 21/22 that could be separated by crystallization and/or flash chromatography on silica gel (Scheme 3). Selective cleavage via the 1,3-oxazol-5(4H)-ones 10a-p gave the corresponding optically pure α,α-disubstituted amino-acid derivatives 11 or
制备了各种各样的环状和开链α,α-二取代的α-氨基酸1a-p。通过与衍生自(S)-苯丙氨酸的手性胺15-18偶联,拆分外消旋N-酰化的α,α-二取代氨基酸,形成非对映异构体19/20或21/22,可以通过结晶和/或快速色谱分离在硅胶上(方案3)。通过1,3-恶唑-5(4 H)-酮10a-p的选择性裂解以高收率得到相应的光学纯α,α-二取代氨基酸衍生物11或12(方案3)。α,α-二取代氨基酸的绝对构型由非对映异构体20、21g',22d的X射线结构确定。