Total synthesis and biological evaluation of potent analogues of dictyostatin: modification of the C2-C6 dienoate region

By exploiting a Still-Gennari olefination of a common C11-C26 aldehyde with a C4-C10 or C1-C10 beta-ketophosphonate, three modified C2-C6 region analogues of the 22-membered Macrolide dictyostatin were synthesised and evaluated in vitro for growth inhibition against a range of human Cancer cell lines, including the Taxol-resistant NCI/ADR-Res cell line. 6-Desmethyldictyostatin and 2,3-dihydrodictyostatin displayed potent (low nanomolar) antiproliferative activity, intermediate between dictyostatin and discodermolide, while 2,3,4,5-tetrahydrodictyostatin showed activity comparable to discodermolide. As with dictyostatin, these simplified analogues act through a mechanism of microtubule stabilisation, G2/M arrest and Apoptosis.