Enantiospecific Formation of <i>Trans</i> 1,3-Disubstituted Tetrahydro-β-carbolines by the Pictet−Spengler Reaction and Conversion of <i>Cis</i> Diastereomers into Their <i>Trans</i> Counterparts by Scission of the C-1/N-2 Bond
作者:Eric D. Cox、Linda K. Hamaker、Jin Li、Peng Yu、Kevin M. Czerwinski、Li Deng、Dennis W. Bennett、James M. Cook、William H. Watson、Mariusz Krawiec
DOI:10.1021/jo951170a
日期:1997.1.1
experiments in TFA. Conversion of the cis diastereomers into the more stable trans diastereomers is believed to occur under acidic conditions by cleavage of the carbon (C-1)-nitrogen (N-2) bond with complete retention of configuration at the C-3 stereocenter. Evidence from deuterium exchange experiments as well as optical rotations support this model for epimerization. In addition, when cis diastereomer
影响反式-1-烷基-2-苄基-3-(烷氧羰基)-1,2,3,4-四氢-β-咔啉和反式-3-(烷氧羰基)-1-烷基-的立体选择性形成的因素通过在非质子和酸性条件下,将色氨酸衍生物与空间位阻不同的醛加热色氨酸衍生物,然后测定Pictet-Spengler环化法制得的2-(二苯基甲基)-1,2,3,4-四氢-β-咔啉顺式至反式非对映体如此形成。在N(b)-氮原子上存在苄基时,当用环己烷甲醛进行环化反应时,该缩合反应的非对映化学结果会改变,从而提供100%的反式立体选择性。此外,当N(b)-(二苯甲基)色氨酸异丙酯与任意大小的醛缩合时,反式非对映异构体以100%的立体选择性形成。如TFA中的平衡实验所示,反式N(b)-取代的非对映异构体在热力学上比其顺式同类物更稳定。据信,顺式非对映异构体向更稳定的反式非对映异构体的转化是在酸性条件下通过裂解碳(C-1)-氮(N-2)键并完全保留C-3立体中心的构