Preparation of Alkyl-Substituted Indoles in the Benzene Portion. Part 14. Synthesis of (.+-.)-Duocarmycin SA, Natural (+)-Duocarmycin SA and Non-natural (-)-Duocarmycin SA.
作者:Hideaki MURATAKE、Itsuko ABE、Mitsutaka NATSUME
DOI:10.1248/cpb.44.67
日期:——
Total synthesis of duocarmycin SA (1), an extremely potent cytotoxic antibiotic, was achieved in the racemic form at first by effectively utilizing two reactions as key steps, (i) an intramolecular Heck reaction of the benzyl ether 21a, derived from a dihydropyridine 13a and a pyrrole derivative 11, to form tricyclic compounds 25a and 26a, and (ii) a modified Mitsunobu reaction on the diol derivative 40 for the construction of compound 41 having the pivotal pharmacophore of a cyclopropanoindolinone partial structure, which is critical for the high biological activities of 1. Next, optical resolution of an intermediary racemic secondary alcohol 50 was cleanly attained by derivatizing it to (R)-O-methylmandelates 52 and 53, and the resulting chiral alcohols (+)-50 and (-)-50 were respectively transformed into unnatural (-)-1 and natural (+)-1. Finally inversion of the secondary alcohol (+)-50 to the enantiomer (-)-50 was effected by using the Mitsunobu reaction. This constitutes an enantio-convergent total synthesis of natural duocarmycin SA (1) starting from a racemic compound.
二氧卡米新SA(1)的全合成首先以外消旋形式实现,通过有效利用两个反应作为关键步骤:(i)从二氢吡啶13a和吡咯衍生物11衍生的苄基醚21a进行的分子内Heck反应,以形成三环化合物25a和26a,以及(ii)对醇衍生物40进行的改进Mitsunobu反应,以构建具有环丙烷吲哚啉酮部分结构的关键药效团的化合物41,这对1的高生物活性至关重要。接下来,通过将中间的外消旋次级醇50衍生化为(R)-O-甲基曼德酸盐52和53,干净地实现了光学分离,得到的手性醇(+)-50和(-)-50分别转化为非天然的(-)-1和天然的(+)-1。最后,通过使用Mitsunobu反应实现了次级醇(+)-50到其对映体(-)-50的倒转。这构成了以外消旋化合物为起始材料的天然二氧卡米新SA(1)的对映体收敛全合成。