Abstract The N′-dabcyl-N α-(9-fluorenylmethoxy)-carbonyllysine was prepared by reaction of lysine-Cu2+ complex with the N-hydroxysuccinimide (HOSu) activated ester of [4-(4'- dimethylamino) phenylazo] benzoic acid (dabcyl acid) followed by treatment with EDTA and acylation with Fmoc-OSu, and the N α-tert-butyloxycarbonyl-N′-dabcyllysine was prepared by reaction of N α-tert-butyloxycarbonyllysine with dabcyl-OSu.