作者:Elias A. Couladouros、Ioanna C. Soufli、Vassilios I. Moutsos、Raj K. Chadha
DOI:10.1002/(sici)1521-3765(199801)4:1<33::aid-chem33>3.0.co;2-8
日期:1998.1
The 15-membered caffrane ring of the natural product group of combretastatins D is synthesized in high yield with suitably functionalized saturated seco acids. The key step is a Mitsunobu-type macrolactonization. A common synthon is used for the construction of both combretastatins. The synthesis of combretastatin D-2 is completed by the use of Sammuelson's dehydroxylation protocol, The asymmetric epoxide of combretastatin D-1 is constructed in two separate operations: one asymmetric center is fixed at an early stage of the synthetic route by Sharpless AD of a trans-styrene derivative, inducing the intramolecular formation of the asymmetric epoxide at the final stages. The synthesis of the title compounds is accomplished in high overall yields (37% for D-1 and 41% for D-2, 9 steps in both cases). X-ray crystallographic analysis of the (S)-(+) acetylmandelic ester of (-)-combretastatin D-1 verified its revised structure.