Maleate salts of bedaquiline

Abstract

Bedaquiline is one of two important new drugs for the treatment of drug-resistant tuberculosis (TB). It is marketed in the US as its fumarate salt, but only a few salts of bedaquiline have been structurally described so far. We present here five crystal structures of bedaquilinium maleate {systematic name: [4-(6-bromo-2-methoxyquinolin-3-yl)-3-hydroxy-3-(naphthalen-1-yl)-4-phenylbutyl]dimethylazanium 3-carboxyprop-2-enoate}, C32H32BrN2O2 +·C4H3O4 −, namely, a hemihydrate, a tetrahydrofuran (THF) solvate, a mixed acetone/hexane solvate, an ethyl acetate solvate, and a solvate-free structure obtained from the acetone/hexane solvate by in situ single-crystal-to-single-crystal desolvation. All salts exhibit a 1:1 cation-to-anion ratio, with the anion present as monoanionic hydromaleate and a singly protonated bedaquilinium cation. The maleate exhibits the strong intramolecular hydrogen bond typical for cis-dicarboxylic acid anions. The conformations of the cations and packing interactions in the maleate salts are compared to those of free base bedaquiline and other bedaquilinium salts.