Bepostastine besylate.

The crystal structure of bepotastine besylate {systematic name: 1-(3-carb-oxy-prop-yl)-4-[(4-chloro-phen-yl)(pyridin-2-yl)meth-oxy]piperidin-1-ium benzene-sulfonate, C21H26ClN2O3 +·C6H5O3S-) was refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory techniques. Bepotastine besylate crystallizes in the space group P1, with a = 8.0153 (6), b = 9.8211 (5), c = 10.2345 (10) Å, α = 88.164 (2), β = 68.962 (2), γ = 65.8917 (8)°, V = 680.149 (1) Å3 and Z = 1 at 298 K. N-H⋯O and O-H⋯O hy-dro-gen bonds link the cations and anions into a chain extending parallel to the c axis, with a graph set C 2 2(11).