An enantioselective route to four tricyclic amino acids and N-tosylamides, composed of a central norbornane framework with a 2-endo,3-endo-annelated pyrrolidine ring and a 5-endo-C1 or -C2 side chain, has been developed. A key intermediate was the chiral, N-Boc-protected ketone (1R,2S,6S,7R)-4-azatricyclo[5.2.1.02,6]decan-8-one, available from inexpensive endo-carbic anhydride in five steps and 47% yield. The rigid scaffold makes these amino acid derivatives promising candidates for β-turn-inducing building blocks in peptidomimetics and for chiral auxiliaries in asymmetric organocatalysis.
一种选择性对映体路线,用于合成由中心去甲基环戊烷骨架组成的四种三环氨基酸和N-对甲苯磺酰胺,其中包含一个2-内、3-内-螺环化吡咯啉环和一个5-内-C1或-C2侧链。已开发出这种路线。关键中间体是手性的N-Boc保护酮(1R,2S,6S,7R)-4-氮杂三环[5.2.1.0^2,6]癸烷-8-酮,可从廉价的内碳酸酐在五个步骤中得到,产率为47%。这种刚性支架使这些氨基酸衍生物成为肽类模拟物中β-转变诱导构建块的有前途候选物,也可用作不对称有机催化中的手性辅助剂。