The invention provides prodrugs of DNA-reactive analogs of duocarmycin and CC-1065 anticancer agents, wherein a cyclic prodrug form, such as carbamate, thionocarbamate, or carbamimidate, can be hydrolyzed by the patient in vivo to yield a respective bioactive agent comprising a DNA-alkylating moiety and a binding/targeting moiety. The DNA-reactive moiety is a &gamma；-spirocyclohexenone fused to a heterocyclyl group which can be produced by endogenous hydrolysis of a cyclic carbamate prodrug of the invention. The cyclic carbamate prodrug produces no residual byproduct during activation in vivo. Methods of synthesis and biological methods and data are also provided.
