Stereospecific Approach to the Synthesis of Ring-A Oxygenated<i>Sarpagine</i>Indole Alkaloids. Total Synthesis of the Dimeric Indole Alkaloid<i>P</i>-(+)-Dispegatrine and Six Other Monomeric Indole Alkaloids
作者:Chitra R. Edwankar、Rahul V. Edwankar、Ojas A. Namjoshi、Xuebin Liao、James M. Cook
DOI:10.1021/jo400469t
日期:2013.7.5
The first regio- and stereocontrolled total synthesis of the bisphenolic, bisquaternary alkaloid (+)-dispegatrine (1) has been accomplished in an overall yield of 8.3% (12 reaction vessels) from 5-methoxy-d-tryptophan ethyl ester (17). A crucial late-stage thallium(III) mediated intermolecular oxidative dehydrodimerization was employed in the formation of the C9–C9′ biaryl axis in 1. The complete stereocontrol
首次以5-甲氧基-d-色氨酸乙酯 ( 17 )为原料,以区域和立体控制的方式全合成双酚、双季铵生物碱 (+)-dispegatrine ( 1 ),总产率为 8.3%(12 个反应容器) 。关键的后期铊 (III) 介导的分子间氧化脱氢二聚作用被用于1中 C9-C9' 联芳轴的形成。在这个关键的联芳基偶联步骤中观察到的完全立体控制是由于单体洛赫那林 ( 6 ) 的天然沙巴碱构型的不对称诱导,并且由 Suzuki 和四氢β-咔啉 ( 35 )的氧化脱氢二聚模型研究证实。。通过X射线晶体学确定了洛赫那林二聚体( 40 )和二胡七碱( 1 )的轴向手性,并确定为P (S)。此外,首次全合成了单体吲哚生物碱 (+)-segatrine ( 2 )、(+)-10-methoxyvelosimine ( 5 )、(+)-lochnerine ( 6 )、lochvinerine ( 7 )、(+)-sarpagine