PROBLEM TO BE SOLVED: To obtain the subject new compound capable of minifesting excellent endothelin receptor antagonism and usable for prevention and treatment of the disease associated with excessive secretions of the endothelins.
SOLUTION: This compound is 4,5-dihydro-[1H]-benz[g]indazole-3-carboxylic acid derivative of formula I (Ar is an aryl; R1 is H, a lower alkyl, an aryl, a cycloalkyl or a heterocyclic group) or a salt thereof, e.g. 4,5-dihydro-1-(3- methoxybenzyl)-7-(5-pyrimidinylmethoxy)-[1H]-benz[g]iondazole-3-carboxylic acid. For example, the compound of formula I is obtained by reacting a compound of formula II (R2 is a lower alkyl) with a hydrazine derivative of formula III or a hydrate or a salt thereof to provide a compound of formula IV, and further hydrolyzing the compound of formula IV. A part of the compound of formula I has an excellent phosphodiesterase III inhibitory effect.