Constituents of rhizoma nupharis. XXVIII. New syntheses of (.+-.)-7-epideoxynupharidine, (.+-.)-1-epi-7-epideoxynupharidine, (.+-.)-deoxynupharidine, and (.+-.)-1-epideoxynupharidine.
作者:SHINGO YASUDA、MIYOJI HANAOKA、YOSHIO ARATA
DOI:10.1248/cpb.28.831
日期:——
A new stereoselective synthesis of (±)-7-epideoxynupharidine (1), the most stable quinolizidine-type Nuphar alkaloid, is described. Condensation of 2-ethyl-5-methylpyridine (5) with acetonitrile, followed by ketalization, gave the ketal (13), which was hydrogenated to afford the piperidine (14). Deketalization of 14 afforded the aminoketone (15). Condensation of 15 with 3-furylaldehyde afforded four quinolizidin-2-ones (8, 16, 17, and 18) in 14, 45, 1, and 3% yields, respectively. The cis-quinolizidines (16 and 18) were isomerized to the trans-quinolizidines (8 and 17, respectively). Wolff-Kishner reduction of 8 afforded (±)-7-epideoxynupharidine (1) (45%) and (±)-1-epi-7-epideoxynupharidine (2) (15%). Similar reduction of 17 provided (±)-deoxynupharidine (3) (33%) and (±)-1-epideoxynupharidine (4) (14%).
本文描述了一种新的立体选择性合成(±)-7-epideoxynupharidine (1)的方法,它是最稳定的喹嗪类 Nuphar 生物碱。2-ethyl-5-methylpyridine (5) 与乙腈缩合,然后进行缩酮化,得到缩酮 (13),缩酮经氢化后得到哌啶 (14)。14 脱酮后得到氨基酮(15)。15 与 3-呋喃甲醛缩合后得到四个喹嗪-2-酮(8、16、17 和 18),产率分别为 14%、45%、1% 和 3%。顺式喹嗪类化合物(16 和 18)被异构化为反式喹嗪类化合物(分别为 8 和 17)。8 的沃尔夫-基什纳还原反应得到了 (±)-7-epideoxynupharidine (1) (45%) 和 (±)-1-epi-7-epideoxynupharidine (2) (15%)。类似地还原 17 得到了 (±)-deoxynupharidine (3) (33%) 和 (±)-1-epideoxynupharidine (4) (14%)。