Carbonic anhydrase activators: synthesis of high affinity isozymes I, II and IV activators, derivatives of 4-(4-tosylureido-amino acyl)ethyl-1H-imidazole (histamine derivatives).

Reaction of histamine (Hst) with tetrabromophthalic anhydride and protection of its imidazole moiety with tritylsulfenyl chloride, followed by hydrazinolysis, afforded N-1-tritylsulfenyl histamine, a key intermediate which was further derivatized at its aminoethyl moiety. Reaction of the key intermediate with 4-tosylureido amino acids/dipeptides (ts-AA) in the presence of carbodiimides, afforded after deprotection of the imidazole moiety, a series of compounds with the general formula ts-AA-Hst (ts=4-MeC(6) H(4) SO(2) NHCO). Some structurally related dipeptide derivatives with the general formula ts-AA1-AA2-Hst, were also prepared, by in a similar way to the amino acyl compounds mentioned above. The new derivatives were examined as activators of three carbonic anhydrase (CA) isozymes, hCA I, hCA II (cytosolic forms) and bCA IV (membrane-bound form). Efficient activation was observed against all three isozymes, but especially against hCA I and bCA IV, with affinities in the 1-10 nanomolar range for the best compounds. hCA II was on the other hand activatable with affinities around 20-50 nM. This new class of CA activators might lead to the development of drugs/diagnostic agents for the CA deficiency syndrome, a genetic disease of bone, brain and kidneys.