General Approach to the Total Synthesis of 9-Methoxy-Substituted Indole Alkaloids: Synthesis of Mitragynine, as well as 9-Methoxygeissoschizol and 9-Methoxy-<i>N</i><sub>b</sub>-methylgeissoschizol
作者:Jun Ma、Wenyuan Yin、Hao Zhou、Xuebin Liao、James M. Cook
DOI:10.1021/jo801839t
日期:2009.1.2
Herein, the full details of the synthesis of the 9-methoxy-substituted Corynanthe indole alkaloids mitragynine (1), 9-methoxygeissoschizol (3), and 9-methoxy-Nb-methylgeissoschizol (4) are described. Initially, an efficient synthetic route to the optically active 4-methoxytryptophan ethyl ester 20 on a multigram scale was developed via a Mori−Ban−Hegedus indole synthesis. The ethyl ester of d-4-methoxytryptophan
这里,9-甲氧基取代的肽的全部细节柯楠因吲哚生物碱帽柱木碱(1),9-methoxygeissoschizol(3),和9-甲氧基Ñ b -methylgeissoschizol(4)进行说明。最初,通过 Mori-Ban-Hegedus 吲哚合成开发了多克规模的光学活性 4-甲氧基色氨酸乙酯20的有效合成路线。d -4-甲氧基色氨酸20的乙酯是通过自由基介导的二氢吲哚12 的区域选择性溴化作为关键步骤获得的。或者,关键的 4-甲氧基色氨酸中间体22可以通过芳基碘化物10b与内部炔烃21a的 Larock 杂环化合成。使用 Boc 保护的苯胺10b对这种异质环化的成功至关重要。α,β-不饱和酯6是通过Pictet-Spengler反应作为关键步骤合成的。随后进行 Ni(COD) 2介导的环化以在 C-15 处建立立体中心。去除31中的苄氧基以提供中间体酯5。该手性四环酯5用于完成9-甲氧基geissoschizol