Zolmitriptan oxalate and zolmitriptan camphorsulfonate: the first structural study of salt complexes of the antimigraine drug zolmitriptan.

Zolmitriptan hydrogen oxalate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium hydrogen oxalate], C16H22N3O2(+)·C2HO4(-), (I), and zolmitriptan camphorsulfonate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium (S,R)-{2-hydroxy-7,7-dimethylbicyclo[2.2.1]heptan-1-yl}methanesulfonate], C16H22N3O2(+)·C10H15O4S(-), (II), are the first reported salt complexes of the antimigraine drug zolmitriptan. Compound (I) crystallizes in the space group P2(1) with two molecules of protonated zolmitriptan and two oxalate monoanions in the asymmetric unit, while compound (II) crystallizes in the space group P2(1)2(1)2(1) with one protonated zolmitriptan molecule and one camphorsulfonate anion in the asymmetric unit. The orientations of the ethylamine side chain and the oxazolidinone ring with respect to the indole ring of the zolmitriptan cation are different for (I) and (II). In (I), they are oriented in opposite directions and the molecule adopts a step-like appearance, while in (II) the corresponding side chains are folded in the same direction, giving the molecule a cup-like appearance. The zolmitriptan molecules of (I) form an R2(2)(8) dimer, while in (II) they form a helical chain with a C(11) motif. The oxalate monoanions of (I) interact with the zolmitriptan cations and extend the dimer into a three-dimensional hydrogen-bonded network. In (II), the camphorsulfonate anion forms an R2(2)(15) ring motif with the zolmitriptan cation.