The crystal and molecular structure of atipamezole base and atipamezole hydrochloride

Crystal structures of alpha₂-adrenergic antagonist atipamezole base (1) and its hydrochloric acid salt (2) have been determined using X-ray diffraction methods. Atipamezole base crystallized in the monoclinic space group P2₁, with unit cell parameters a = 13.238(4), b = 9.747(4), c = 14.609(5) Å, β = 107.75(4)°, V = 1,795.3(12) ų and Z = 6 (three independent molecules of 1). Atipamezole hydrochloride crystallized in the monoclinic space group Cc, with unit cell parameters a = 12.052(1), b = 32.561(9), c = 13.668(5) Å, β = 102.64(1)°, V = 5,233(2) ų and Z = 16 (four independent molecules of 2). Each of the three atipamezole moieties in 1 has an intramolecular C-H⋯;N H-bond. In both structures the molecules are H-bonded to form extended chains.