CRYSTAL-STRUCTURE OF N(1)-METHYL-ALPHA-ISOSPARTEINE IODIDE AND 1,16-ENDOMETHYLENE-ALPHA-ISOSPARTEINE DIIODIDE

The crystal and molecular structures of mono- and di-quaternary salts of alpha-isosparteine have been determined by X-ray analysis. Both N(1)-methyl-alpha-isosparteine iodide and 1,16-endomethylene-alpha-isosparteine diiodide crystallize in the space group C222(1). The N-methylation does not change the configuration of parent trans-cisoid-trans-alpha-isosparteine. The crystallographic twofold symmetry axis coincides with molecular symmetry of the diquaternary cation. The trans-cisoid-trans-1,16-endomethylene-alpha-isosparteine diiodide and its stereoisomer, trans-cisoid-cis-1,16-endomethylenesparteine diiodide, form isomorphous crystals. Short cation-anion contacts in crystal structures suggest existence of C-H ... I- hydrogen bonds in the solid state. In the N(1)-methyl-alpha-isosparteine iodide crystal, 7 C ... I- distances in the range 3.85-4.15 angstrom have been found, while 17 distances of this type have been observed in 1, 16-endomethylene-alpha-isosparteine diiodide.