New asymmetric route to bridged indole alkaloids: formal enantiospecific syntheses of (−)-suaveoline, (−)-raumacline and (−)-N b-methylraumacline
作者:Patrick D. Bailey、Ian D. Collier、Sean P. Hollinshead、Madeleine H. Moore、Keith M. Morgan、David I. Smith、John M. Vernon
DOI:10.1039/a606081a
日期:——
The homologous nitrile 13 derived from
L-tryptophan undergoes a modified
Pictet–Spengler reaction with methyl propynoate, under conditions
of kinetic control, to afford the
cis-tetrahydro-β-carboline 15a
(cis∶trans =
77∶23). After protection, Dieckmann–Thorpe cyclisation to
the bridged keto nitrile 20 proceeds in 90% yield. Simple functional
group modifications via the alcohol 21a and nitrile 22
(structures confirmed by X-ray crystallography) allow convergence with
the tetracyclic α,β-unsaturated aldehyde 10, which is an
advanced intermediate for the synthesis of a range of bridged indole
alkaloids.
同系腈 13 衍生自
L-色氨酸经过修饰
在一定条件下与丙酸甲酯发生 Pictet-Spengler 反应
动力学控制,以提供
顺式四氢-β-咔啉15a
(顺式∶反式=
77∶23)。保护后,Dieckmann-Thorpe 环化
桥接酮腈20的产率为90%。简单实用
通过醇 21a 和腈 22 进行基团修饰
(通过 X 射线晶体学证实的结构)允许收敛
四环α,β-不饱和醛10,它是
用于合成一系列桥联吲哚的高级中间体
生物碱。