Graduate School of Pharmaceutical Sciences, The University of Tokyo , Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Org Lett. 2018 Jan 5;20(1):130-133. doi: 10.1021/acs.orglett.7b03482. Epub 2017 Dec 12.
The steroidal ABCD-ring system of the potent neurotoxin batrachotoxin was efficiently assembled in a convergent fashion. Bridgehead radical coupling between the simple AB-ring and D-ring fragments (3 and 4) formed the sterically congested linkage at the C9-oxygen-attached tetrasubstituted carbon. The C-ring was then cyclized by the Pd/Ni-promoted Ullmann reaction of the vinyl triflate and vinyl bromide of 19, giving rise to tetracyclic structure 1.
高效地以汇聚方式组装了强效神经毒素蛙毒素的甾体 ABCD-环系统。简单的 AB 环和 D 环片段（3 和 4）之间的桥头自由基偶联形成了在 C9-氧连接的四取代碳处的空间拥挤键。然后，C 环通过 Pd/Ni 促进的 19 的乙烯三氟甲磺酸酯和乙烯溴化物的乌尔曼反应环化，生成四环结构 1。
