Kadota Isao, Takamura Hiroyoshi, Nishii Hiroki, Yamamoto Yoshinori
Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
J Am Chem Soc. 2005 Jun 29;127(25):9246-50. doi: 10.1021/ja051171c.
The convergent total synthesis of brevetoxin B (1) has been achieved. The intramolecular allylation of the O,S-acetal 20, prepared from the alpha-chlorosulfide 17 and the alcohol 5, was carried out using AgOTf as a Lewis acid to give the diene 21, predominantly. Ring-closing metathesis of 21 with the Grubbs catalyst 23 afforded the hexacyclic ether 25 which was converted to the A-G ring segment 2 through several steps. The intramolecular allylation of the alpha-acetoxy ether 42, prepared from 2 and the J-K ring segment 3, followed by ring-closing metathesis provided the polycyclic ether framework 44. A series of reactions of 44, including oxidation of the A ring, deprotection of the silyl ethers, and selective oxidation of the resulting allylic alcohol, furnished 1.
短裸甲藻毒素B（1）的汇聚式全合成已完成。由α-氯硫化物17和醇5制备的O,S-缩醛20的分子内烯丙基化反应，以三氟甲磺酸银作为路易斯酸进行，主要生成二烯21。21与格拉布催化剂23进行闭环复分解反应得到六元环醚25，其经几步反应转化为A - G环片段2。由2和J - K环片段3制备的α-乙酰氧基醚42进行分子内烯丙基化反应，随后进行闭环复分解反应，得到多环醚骨架44。44的一系列反应，包括A环的氧化、硅醚的脱保护以及所得烯丙醇的选择性氧化，得到了1。
