Structure of the antiplasmodial compound 7,9-dinitrocryptolepine hydrochloride methanol solvate.

Abstract

The structure of C16H10N4O4[HCl,1.5CH3OH], Mr = 406.80, has been determined from X-ray diffraction data. The crystals are monoclinic, space group C2/c, with eight molecules per unit cell and a = 21.482(4), b = 7.131(1), c = 24.495(5) A ° , b = 111.01(3) , crystal density Dc = 1.546 g/cm3. The material was difficult to crystallize and crystals produced were found to be poor diffractors. Intensity data were measured at liquid nitrogen temperature using a weakly diffracting crystal typical of the batch. However the X-ray analysis has finally enabled the chemical constitution of this cryptolepine derivative, which was previously incorrectly assigned, to be unequivocally established. Direct methods were used to solve the structure which was refined by full-matrix least squares to a conventional R-index of 0.0798 for 2,861 reflections and 268 parameters. The 7,9-dinitrocryptolepine molecule is highly planar with a strong intramolecular hydrogen bond between N(10) in ring C and O(92) of a nitro group. There are a number of intermolecular hydrogen bonds involving the cryptolepine derivative the hydrochloride and both solvated methanols. One of the methanol solvate molecules (methanol 2) is unusually disordered with its C atom lying exactly on a crystallographic twofold axis. Consequently the methanol OH and H3 groups are at 0.5 occupancy and repeated by the twofold symmetry.