1,6-Dihydro-3(2H)-pyridinones. III. A formal synthesis of (.+-.)-catharanthine.
作者:TAKESHI IMANISHI、NORIYUKI YAGI、HIROAKI SHIN、MIYOJI HANAOKA
DOI:10.1248/cpb.30.4052
日期:——
On treatment with ethyl vinyl ether containing mercuric acetate, the allylic alcohol (5) afforded the aldehyde (7), which was acetalized to 8. Hydroboration-oxidation of 8 was followed by pyridinium chlorochromate (PCC) oxidation to yield two isomeric ketones (11 and 12), of which the former was subjected to acidic hydrolysis to afford the 2-azabicyclo [2. 2. 2] octanone (3b) in excellent yield. On the other hand, the diketal (22) derived from 11 also gave the N-benzyloxycarbonyl analogue (3c) on acidic treatment. Ketalization of 3c and subsequent oxidation provided the ketone (27), which was transformed into the amide (29) via the amine (28). Cyclization of 29 furnished the pentacyclic product (30), which has already been converted into (±)-catharanthine (4) and (±)-velbanamine (31).
用含有醋酸巯基的乙烯基乙醚处理烯丙基醇(5)后,得到醛(7),醛(7)经乙缩醛生成 8。8 经过氢硼氧化和吡啶鎓氯铬酸盐(PCC)氧化后得到两个异构酮(11 和 12),其中前者经过酸性水解后得到 2- 氮杂双环 [2. 2. 2] 辛酮(3b),收率极高。另一方面,由 11 衍生出的二酮(22)经酸性处理后也得到了 N-苄氧羰基类似物(3c)。3c 的缩酮化和随后的氧化反应生成了酮 (27),并通过胺 (28) 转化为酰胺 (29)。29 环化后得到五环产物 (30),该产物已转化为 (±)- 卡塔兰碱 (4) 和 (±)-velbanamine (31)。