甲基乙基丙二酸的不对称酯化反应

The Asymmetric Esterification of Ethylmethylmalonic Acid

由甲基乙基丙二酸与l-薄荷醇的单酯化反应产物(Ⅰ)经酰氯(Ⅱ)转变为酰胺(Ⅲ),(Ⅲ)经皂化得到部分光学活性的甲基乙基丙二酸氢酰胺(Ⅳ),(Ⅳ)经Hoffmann降解得到部分光学活性的2-甲基-2-氨基丁酸(V).

Ethylmethylmalonic acid reacted with l-menthol to form the diastereo-meric l-menthyl hydrogen ethylmethylmalonates(Ⅰ).From(Ⅰ)the diaster-eomeric l-menthyl ethylmethylmalonamides(Ⅲ)were obtained in nearly quantitative yield.To saponify the amides(Ⅲ)with alkali,the partially optically active ethylmethylmalonanic acid(Ⅳ)were produced in 70%yield.(Ⅲ)were degraded to partially optically active a-amino-methylethylacetic acid(Ⅴ)(V,8.8%e.e S-(+)-isomer)by the Hoffmann degradaton.In DMF the monobrucine salts of ethylmethylmalonic acid reacted with iodoethane and diazomethane to produce the optically inactive mono-ethyl ester(Ⅵ)and monomethyl ester(Ⅴ)respectively.