(8). Since enantiomerically pure 4 has been previously converted in five steps by Ireland into (+)-tirandamycic acid (3) and more recently by Schlessinger into (-)-tirandamycin A (1), this achievement constitutes in a strictly formal sense the total syntheses of these substances. The key step in the synthesis of 4 features the transformation of the enantiomerically pure furfuryl diol 25 into 29 by
2,9-二氧杂双环[3,3,1]
壬烷4的有效,不对称合成是在9个
化学步骤中由4,5-二甲基
呋喃甲醛完成的(8)。由于对映体纯4先前已由爱尔兰分五步转化为(+)-丁达酰胺酸(3),最近又由Schlessinger转化为(-)-丁达霉素A(1),因此从严格的形式上讲,该成就构成了总合成物这些物质。合成4的关键步骤是通过(
呋喃环的)初始选择性氧化和随后的酸催化双环
缩酮化,将对映体纯的糠基二醇25转变为29。