STRUCTURE OF THE ANTIMALARIAL (+/-)-MEFLOQUINE HYDROCHLORIDE

(11R*,12S*)-(+/-)-alpha-2-Piperidinyl-2,8-bis-(trifluoromethyl)-4-quinolinemethanol monohydrochloride, C17H17F6N2O+.Cl-.0.5CH3OH, M(r) = 430.8, tetragonal, P4(2)/n (origin at center of symmetry), a = b = 24.595 (4), c = 6.398 (2) angstrom, V = 3870.0 angstrom 3, Z = 8, D(x) = 1.48 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 24.28 cm-1, F(000) = 1768, room temperature, final R = 7.5% for 2067 reflections with \F(o)\ > 3-sigma(F). Mefloquine hydrochloride crystallized as a secondary amine salt with channels of disordered methanol solvent. The trifluoromethyl group on the C adjacent to the quinoline N atom exhibited rotational disorder. Each chloride ion accepts three hydrogen bonds, one each from the hydroxyl group and the two H atoms of the amine group of mefloquine from three separate molecules. The angle between the average plane of the quinoline ring and the average plane of the piperidine ring is 110.5-degrees.