Design, Synthesis and Evaluation of Imidazolylmethyl Carbamate Prodrugs of Alkylating Agents

Two approaches to prodrugs of alkylating agents based on an imidazolylmethyl carbamate nucleus were explored. A 2-azido analogue (3) of the bis-carbamate carmethizole (1) displayed similar aerobic cytotoxicity to 1 in a panel of human and murine cell lines. Approaches to the 2-amino and 2-carbamoyl analogues are described. In the second approach an imidazolylmethanol was used as a ‘trigger’ linked via a carbamate to the alkylating agent N,N-bis(2-chlorethyl)amine (BCEA). Nitroimidazole and methylsulphinylimidazole carbamate prodrugs 6–8 were 5–20-fold less toxic than BCEA. Despite this deactivation in the prodrug form, little increase in cytotoxicity was observed under hypoxia. The data suggest that BCEA released on bioreduction is not sufficiently potent to contribute significant additional cytotoxicity.