Conformationally rigid polyheterocycles 14a,b which mimic the putative receptor-bound conformation of dihydropyridine type calcium channel modulators are prepared in a six-step reaction sequence starting from urea, ethyl acetoacetate and 2-alkenylbenzaldehydes. The key step in the synthesis involves the regio- and diastereoselective intramolecular 1,3-dipolar cycloaddition reaction of a dihydropyrimidine-fused isomünchnone dipole. Deprotection of the CBZ-protected intermediates 13a,b leads to the desired target molecules 14a,b. Prolonged exposure of these cyclic enamines in solution to the atmosphere results in oxidation to the corresponding α-hydroxy imines 16a,b. Catalytic hydrogenation of the related N-benzyl-protected polycycle 19 furnishes the fully saturated hexahydropyrimidine derivative 20. The relative stereochemistry in 20 was established by an X-ray crystallographic analysis.
以
尿素、
乙酰乙酸乙酯和 2-烯基
苯甲醛为起始原料,通过六步反应顺序制备出模仿
二氢吡啶类
钙通道调节剂受体结合构象的构象刚性多杂环 14a,b。合成的关键步骤是对二氢
嘧啶融合的异¼nchnone 二极进行区域和非对映选择性分子内 1,3-二极环加成反应。对 C
BZ 保护的中间体 13a,b 进行脱保护处理后,可得到所需的目标分子 14a,b。这些环烯胺在溶液中长时间暴露于大气中会氧化成相应的δ-羟基
亚胺16a,b。对相关的 N-苄基保护多环 19 进行催化氢化,可得到完全饱和的六氢
嘧啶衍
生物 20。通过 X 射线晶体分析确定了 20 的相对立体
化学结构。