N-(omega-Bromoalkyl)-amino acidderivatives, readily prepared from natural alpha-amino acids, gave cyclic amino acids with a quaternary stereocenter by treatment with potassium hexamethyldisilazaide in DMF. The chirality of parent amino acids was almost completely preserved during an enolate-formation and cyclization process, giving aza-cyclic amino acids in up to 98% ee in retention of configuration
N-(ω-溴烷基)-氨基酸衍生物,很容易从天然α-氨基酸制备,通过在DMF中用六甲基二硅氮杂钾处理得到具有季立体中心的环状氨基酸。在烯醇化物形成和环化过程中,亲本氨基酸的手性几乎完全保留,使氮杂环氨基酸的构型保留率高达 98% ee。该方法适用于氮杂环丁烷、吡咯烷、哌啶和氮杂环庚烷衍生物的不对称合成。不对称环化似乎是通过轴向手性烯醇中间体而不是通过协调一致的 SEi 过程进行的。