Synthesis of α-ketols by functionalization of captodative alkenes and divergent preparation of heterocycles and natural products
摘要:
Captodative alkene 1-acetylvinyl p-nitrobenzenecarboxylate 1a was evaluated for its reactivity in Lewis acid-catalyzed Michael additions with functionalized benzene rings and heterocycles, leading to diverse conjugated addition adducts. The hydrolysis of the latter resulted in the desired functionalized a-ketols, including natural alkaloid actinopolymorphol B (24a). The alpha-ketol core structure of these compounds was used as the building block for the synthesis of the natural alkaloid tanakine (25) and for the divergent construction of highly substituted heterocycles, such as 4-oxazolin-2-ones and butenolides, and their respective fused polycyclic derivatives. (C) 2015 Elsevier Ltd. All rights reserved.
描述了天然存在的呋喃衍生物地黄酮 A、B 和 C 的合成。为制备这些天然产物开发了多种替代合成策略。在路易斯酸催化下,呋喃与捕获的烯烃 1-乙酰基乙烯基 4-硝基苯甲酸酯共轭加成得到相应的加合物,分别通过三步和两步转化为地黄酮 B 和 C。它们还通过丙酮与关键的呋喃-2-碳水化合物-醛中间体缩合制备,这些中间体可以很容易地从 D-果糖中获得。双呋喃地黄酮 A 不仅通过丙酮与 5-(甲氧基甲基)呋喃-2-甲醛的双重缩合在一步程序中获得,而且通过将后者与地黄酮 B 以高总产率缩合获得。