Structure of 8-chloro-2-[2-(diethylammonio)ethyl]-2H-[1]benzothiopyrano[4,3,2-cd]indazole-5-methanol monomethanesulfonate. An antischistosomal analog of hycanthone

Abstract

The crystal and molecular structure of the title compound, C20H2aC1NaOS + CH3SO3-, has been determined by X-ray analysis of three-dimensional counter data up to a 20 value of 125 o with Cu Ka radiation. The crystals are triclinic, space group Pi, with Z = 2 and cell parameters a = 8.7282 (8), b = 11.444 (2), c = 12.338 (2)/~, a = 111.71 (1), fl = 94.28 (1) and 7 = 99.68 (1) °. The structure, solved by the standard heavy-atom technique, was refined by the full-matrix least-squares method to R(F) = 0.049 based on 2813 reflections (corrected for absorption) with F 2 > 3a(F2). All H atoms were located, but some were not refined. E.s.d.'s of bond lengths and bond angles involving only C, N and O atoms are of the order of 0.005 A and 0.3 ° . The molecular parameters are all within the range of expected values. The whole fused four-ring system can be regarded as nearly planar. The diethylaminoethyl side chain, protonated at N, has a conformation distinctly different from that in the crystal of hycanthone methanesulfonate, thus demonstrating the conformational lability of this portion of the molecule. The proton attached to the terminal N and the hydroxyl H atoms are hydrogen bonded to two different O atoms of two neighboring methanesulfonate anions. The methanesulfonate anion, which has an expected Car symmetry, in turn furnishes two of its three O atoms as acceptors in the network of interionic hydrogen bonds with two neighboring cations of the title compound, thus forming an infinite hydrogen-bonded chain in the b direction.