The condensation reaction of 3-benzyloxy-4-hydroxybenzaldehyde with 2, 3-epoxy-3- [(3, 4-dimethoxymethoxy) phenyl] -1-propanol, prepared from caffeic acid in four steps, afforded the ether (11) in good yield. Mesylation of 11 followed by treatment with potassium carbonate, provided the epoxide (13), which was converted to the debenzylation product (14) by hydrogenolysis. Compound 14 underwent cyclization with potassium carbonate to yield the trans dioxane derivative (15). Reaction of 15 with the ylide (16) followed by hydrolysis furnished americanin A (1). Isoamericanin A (3) was similarly synthesized from another condensation product (18).
3-苄氧基-
4-羟基
苯甲醛与 2,3-环氧-3-[(3,4-二甲氧基甲氧基)苯基] -1-
丙醇(由
咖啡酸分四步制备)发生缩合反应,得到醚(11),收率很高。对 11 进行中间化,然后用
碳酸钾处理,得到
环氧化物 (13),通过氢解将其转化为去苄基化产物 (14)。化合物 14 与
碳酸钾发生环化反应,生成反式
二恶烷衍
生物(15)。15 与
酰亚胺(16)反应,然后
水解,得到美洲茄素 A(1)。从另一种缩合产物 (18) 中同样合成了异美利坚素 A (3)。