Preparation of Alkyl-Substituted Indoles in the Benzene Portion. Part 11. Total Synthesis of (6R,8S)-Herbindole A, (6R,8S)-Herbindole B, (6R,8S)-Herbindole C, (6R,8S)-cis-Trikentrin A, (6R,8S)-cis-Trikentrin B, (6R,8R)-trans-Trikentrin B, and (6R,8R)-iso-trans-Trikentrin B. Determination of the Absolute Structures of Natural Herbindoles and Trikentrins.
作者:Hideaki MURATAKE、Atsushi MIKAWA、Takako SEINO、Mitsutaka NATSUME
DOI:10.1248/cpb.42.854
日期:——
The key intermediate, (3R, 5S)-3, 5-dimethyl-1-cyclopentenylmethanol (13) for chiral syntheses of herbindoles and trikentrins, was prepared from the known Dields-Alder adduct 12. Employing pertinent methodologies developed in the previous model study (preceding paper), the title herbindoles 31, 34, and 38 as well as trikentrins 4, 6, 41, and 47 having (6R, 8S)- or (6R, 8R)-absolute configuration of the dimethyl groups on the 1, 6, 7, 8-tetrahydrocyclopent[g]indole moiety were synthesized starting from 13 by way of precursor compounds 24b, 27a, and 27b for the crucial indole cyclization reaction. The following results were also obtained. (i) The proposed chemical structures of three herbindoles were confirmed. (ii) The absolute structures of herbindole A and trans-trikentrin B were established to be 1 and 7 by directly comparing optical properties between synthetic materials and the natural products. (iii) The absolute structures of herbindole B (2) and herbindole C (3) were assumed by analogy with 1. (iv) The absolute structures of cis-trikentrin B (6) and iso-trans-trikentrin B (8) were estimated by a circular dichroism (CD) analysis study. (v) Our previous proposal for the absolute configuration of cis-trikentrin A (4) was further confirmed.
(3R, 5S)-3,5-二甲基-1-环戊烯基甲醇 (13) 是手性合成草本吲哚和三炔诺酮的关键中间体,由已知的 Dields-Alder 加合物 12 制备而成。利用之前的模型研究(上一篇论文)中开发的相关方法,以 13 为起点,通过前体化合物 24b、27a 和 27b,合成了 1、6、7、8-四氢环戊[g]吲哚分子上二甲基具有 (6R, 8S)- 或 (6R, 8R)- 绝对构型的标题草吲哚 31、34 和 38 以及三吲哚 4、6、41 和 47,并进行了关键的吲哚环化反应。结果如下(i) 确认了三种草本吲哚的化学结构。(ii) 通过直接比较合成材料和天然产物的光学性质,确定了草本吲哚 A 和反式三尖杉酯素 B 的绝对结构为 1 和 7。(iv) 通过圆二色性(CD)分析研究,估计了顺式三聚氯氰菊酯 B(6)和异反式三聚氯氰菊酯 B(8)的绝对结构。(v) 进一步证实了我们先前提出的顺式三聚氰酸酯 A(4)的绝对构型。