Enantioselective Total Synthesis and Correction of the Absolute Configuration of Megislactone.
Enantioselective Total Synthesis and Correction of the Absolute Configuration of Megislactone.
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甲吉内酯的对映选择性全合成和绝对构型校正。
DOI：
10.1002/chin.200839203
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Yikang Wu
中科院分区：
文献类型：
--
作者：
Guobao Ren;Yikang Wu
标题化合物为大叶九蕊菊的化学成分之一，已合成了对映体纯的形式。通过手性助剂诱导的不对称羟醛缩合反应，在C-2和C-3构建了立体异构中心，C-4由相应的光学活性乳酸酯衍生。侧链中的碳-碳双键使用Suzuki偶联从纯顺式乙烯基碘衍生而来，所述Suzuki偶联与从相应的末端烯烃原位形成的烷基硼烷。在用CAN脱保护TBS基团的过程中，观察到长烷基链中孤立的C-C双键的先前未知的（部分）顺式到反式转化。有些出乎意料的是，在内酯环的存在下，在H-1和C-13 NMR中清楚地揭示了长烷基链中远程双键的反式异构体的另外不可检测的共存。目前的工作明确表明，天然化合物的绝对构型是最初报道的对映体。对以前H-1和C-13 NMR谱线归属中的一些错误也作了修正。(c)2008爱思唯尔有限公司版权所有。
The title compound, one of the constituents from Iryanthera megistophylla, has been synthesized in enantiopure forms. The stereogenic centers at C-2 and C-3 were constructed by using a chiral auxiliary induced asymmetric aldolization and the C-4 was derived from the corresponding optically active lactates. The carbon-carbon double bond in the side chain was derived from a pure cis vinyl iodide using a Suzuki coupling with an alkyl borane formed in situ from the corresponding terminal alkene. A previously unknown (partial) cis to trans transformation of an isolated C-C double bond in a long alkyl chain was observed during the deprotection of TBS group with CAN. Somewhat unexpectedly, the otherwise undetectable co-presence of the trans isomer of the remote double bond in a long alkyl chain was clearly revealed in H-1 and C-13 NMR in the presence of a lactone ring. The present work unambiguously shows that the absolute configuration of the natural compound is the antipode of the one originally reported. Some errors in the previous H-1 and C-13 NMR sinal assignments are also corrected. (c) 2008 Elsevier Ltd. All rights reserved.