Structure−Activity Studies of Urea, Carbamate, and Sulfonamide Derivatives of Acylfulvene

Illudin S and M (1, 2) are highly toxic sesquiterpenes found in the basidiomycete Omphalotus illudens. Illudins have a low therapeutic index, but acylfulvene derivatives display potent in vivo antitumor activity against a variety of multidrug resistant tumors. The lead acylfulvene (4), irofulven (5), in a randomized phase IIB clinical trial significantly increased overall survival in patients with metastatic hormone-refractory prostate cancer who failed prior treatment with two different standard chemotherapeutic regimens. Irofulven is unique, as the primary allylic hydroxyl group can undergo displacement with a variety of nucleophiles to produce analogues that retain key functional groups required for biological activity including the reactive cyclopropylmethyl carbinol and alpha,beta-unsaturated ketone. As described here, we synthesized a variety of urea, carbamate, and sulfonamide derivatives that retain key functional groups and display potent biological activity toward target solid tumor cells in vitro but are relatively nontoxic toward a nontarget B-cell derived cell line.