Structural Studies of Histamine H1 Effector Molecules: The Crystal Structure of the Antihistamine Drug (+)-Chlorpheniramine Maleate; [(+)-S-1-(p-Chlorophenyl)-1-(2-pyridyl)-3-N,N-dimethylpropylamine maleate]

Abstract

Dextrorotatory chlorpheniramine maleate crystallizes from warm ethyl acetate in a P21 cell containing two formula units of the salt, with unit cell dimensions; a = 5.7669(4) Å, b = 20.338(2) Å, c = 9.1347(8) Å, β = 103.73(2)°. Diffractometer data were collected with CuKα radiation to 2θ = 128°. The structure was solved and refined to R = 0.050 and wR = 0.066. The absolute configuration is confirmed as being S. The alkylamine chain is asymmetrically disposed to the two aryl rings, the p-chlorophenyl ring being more exposed and the 2-pyridyl ring partially occluded. The molecule has an open side to which both hydrogen bond and π orbital overlap linkages can occur. The maleate mono-anion is hydrogen bonded to the dimethylamino group via a normal [Formula: see text]linkage. The intramolecular hydrogen bond of the maleate ion is 2.444(5) Å long and is asymmetric.