Conformationally Constrained 7-Azabicyclo[2.2.1]heptane Amino Acids. Synthesis of a Glutamic Acid Analogue
作者:Barry P. Hart、Henry Rapoport
DOI:10.1021/jo982327c
日期:1999.3.1
tert-butyl 7-benzyloxycarbonyl-7-azabicyclo[2.2.1]-2-heptene-1-carboxylate (20). Selective functionalization at C-2 was accomplished by the direct reduction with SmI(2) of 2-keto-3-silyl ether 23 to the C-2 ketone 24, which was converted to alpha,beta-unsaturated ester 25. Stereospecific reduction of the double bond from the exo face leads to a single protected glutamate analogue, tert-butyl (1S,2R,4R)
我们报道了从L-丝氨酸2-取代的7-氮杂双环[2.2.1]庚烷谷氨酸类似物27的合成。半胱氨酸中间体2可通过串联的Wittig / Michael反应转化为2S,3S,5S-三取代的吡咯烷3或通过碘磺酰胺化反应转化为2S,3S,5R-三取代的吡咯烷4。形成[2.2.1]环系统的关键跨环烷基化步骤涉及甲硅烷基醚的β-消除,然后环化以提供7-苄氧基羰基-7-氮杂双环[2.2.1] -2-庚烯-1叔丁基-羧酸盐(20)。在C-2处的选择性官能化是通过将SmI(2)的2-酮-3-甲硅烷基醚23直接还原为C-2酮24来实现的,C-2酮24转化为α,β-不饱和酯25。来自exo脸的双键导致单个受保护的谷氨酸类似物,