[reaction: see text] The syntheses of the cytotoxic natural product pachastrissamine and its unnatural 4-epi-congener were accomplished starting from a natural phytosphingosine. The relatively unstrained cyclic sulfate intermediate smoothly underwent the 5-endo cyclization to yield the 2,3,4-trisubstituted tetrahydrofuran ring system of pachastrissamine. The corresponding epoxy alcohol afforded the
[反应:见正文]细胞毒性
天然产物Pachastrissamine及其非天然的4-epi-同源物的合成是从天然的
植物鞘氨醇开始的。相对未应变的环状
硫酸盐中间体顺利地进行了5内环化,生成了2个3,4,4-三取代的
四氢呋喃环糊精。相应的环氧醇通过
甲苯磺酸酯介导的双转化过程提供了4-表异构体。