Synthesis and Biological Activity of 12-Aza-Epothilones (Azathilones) – Non-Natural Natural Products with Potent Antiproliferative Activity

Abstract

12-Aza-epothilones ('Azathilones') 1 and 2 have been prepared through ring-closing olefin metathesis or macrolactonization-based cyclization reactions. While RCM of the respective dienes 9 and 12 was found to be very effective and produced macrocyclic olefins with high E selectivity, the subsequent reduction of the 9,10-double bond proved to be unexpectedly difficult and low-yielding. Preparation of azathilone 2 was also accomplished via macrolactonization and this approach was found to be more effective. Compound 2 is a highly potent inhibitor of human cancer cell growth in vitro. The activity of this analog is comparable with that of Epo A, both in terms of cytotoxicity against drug-sensitive human cancer cells as well as its tubulin-polymerizing activity. However, in contrast to Epo A, 2 is considerably less potent against multidrug-resistant cancer cells.