Mulzer Johann, Pichlmair Stefan, Green Martin P, Marques Maria M B, Martin Harry J
Institute of Organic Chemistry, University of Vienna, Waehringerstrasse 38, A-1090 Vienna, Austria.
Proc Natl Acad Sci U S A. 2004 Aug 17;101(33):11980-5. doi: 10.1073/pnas.0401503101. Epub 2004 Jul 26.
The convergent synthesis of a benzofuran analog of the carbacyclic ansa compound kendomycin has been achieved by assembling three major fragments by means of epoxide opening and directed ortho lithiation. The crucial tetrahydropyran ring was formed by a highly stereoselective cationic cyclization. Analysis of all synthesized tetrahydropyran-arene compounds reveals a hindered sp(2)-sp(3) rotation, which results in rotational isomers or atropisomers affecting macrocyclization reactions. The latter could only be achieved by means of Horner-Wadsworth-Emmons olefination.
通过环氧化物开环和定向邻位锂化组装三个主要片段,实现了碳环ansa化合物肯多霉素的苯并呋喃类似物的汇聚合成。关键的四氢吡喃环是通过高度立体选择性的阳离子环化形成的。对所有合成的四氢吡喃 - 芳烃化合物的分析表明,存在受阻的sp(2)-sp(3)旋转,这导致旋转异构体或阻转异构体影响大环化反应。后者只能通过霍纳尔 - 沃兹沃思 - 埃蒙斯烯化反应来实现。