Maleate salts of bedaquiline

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-meth-oxy-quinolin-3-yl)-3-hy-droxy-3-(naphthalen-1-yl)-4-phenyl-but-yl]di-methyl-aza-nium 3-carb-oxy-prop-2-enoate}, C₃₂H₃₂BrN₂O₂ ⁺·C₄H₃O₄ ^-, namely, a hemihydrate, a tetra-hydro-furan (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 hydro-maleate and a singly protonated bedaquilinium cation. The maleate exhibits the strong intra-molecular hydrogen bond typical for cis-di-carb-oxy-lic acid anions. The conformations of the cations and packing inter-actions in the maleate salts are compared to those of free base bedaquiline and other bedaquilinium salts.