The title compound (with the systematic name 2-{[(1S)-1-(methoxycarbonyl)-3-methylbutyl]aminocarbonyl}benzoic acid), C15H19NO5, crystallizes in the monoclinic space group P2(1), with two independent molecules per asymmetric unit. The most notable difference between the two molecules is in the dihedral angles between the planes of the carboxyl group and the benzene ring, which are 3.5 (3) and 25.7 (1) degrees . This difference may account for the fact that two competing reactions are observed in aqueous solution, namely cyclization to form the imide N-phthaloylleucine and hydrolysis of N-(2-carboxybenzoyl)-L-leucine methyl ester to phthalic acid and leucine.