A simple approach to several derivatives of pipecolic acid is via a multicomponent reaction starting from cyclic imines 2, which are synthesized on a large scale and with different substitution patterns. The protected amino acids 3 are formed in high yields. In cases where chiral imines are used the target compounds are obtained with remarkable diastereoselectivity. Bisamides 3 serve as versatile precursors for the preparation of a wide range of amino acid derivatives. Different methods of hydrolysis of 3 lead to the free pipecolic acids or its derivatives. Employment of methanol or ethanethiol as a nucleophile in the acid-mediated conversion of enamides 3 results in N-acylated amino acid esters 5. Furthermore a method for the resolution of the obtained racemic α-amino acids via diastereomeric salt formation is described.
一种简单的方法用于多种派克酸衍
生物的合成,是通过从环状
亚胺2开始的多组分反应,这些环状
亚胺可以大规模合成并具有不同的取代模式。保护的
氨基酸3以高产率生成。当使用手性
亚胺时,目标化合物以显著的非对映体选择性获得。双酰胺3作为多功能的前体,用于制备多种
氨基酸衍
生物。对3的不同
水解方法可以生成游离的派克酸或其衍
生物。在酸介导下,使用
甲醇或
乙硫醇作为亲核试剂对烯酰胺3进行转化,得到N-酰基
氨基酸酯5。此外,还描述了一种通过非对映体盐形成来分离获得的外消旋
α-氨基酸的方法。