A wide range of compounds containing a weak oxy acid (with a pK_a between 3 and 7), including carboxylates, phenols, and phosphates can be reacted with 1-(4,5-dimethyoxy-2-nitrophenyl)diazoethane to form the 1-(4,5-dimethyoxy-2-nitrophenyl)ethyl (DMNPE)-caged analog. The DMNPE Generation Kit provides the reagents for generating the unstable diazoethane and the subsequent preparation of photoactivatable DMNPE esters.