Crystal and molecular structure of histamine H₂-receptor antagonists of the ranitidine family. Part 1. 1-(5-dimethylaminomethyl)- furfurylthiopropan-2-one thiosemicarbazone and 1-(5-dimethylaminomethyl) furfurylthiopropan-2-one 1-methylamino-2-nitroethenylhydrazone

The crystal and molecular structures of the title compounds have been determined by X-ray analysis. The crystals of the thiosemicarbazone derivative (RANTS) are monoclinic, P2₁/n, Z = 4, a = 10.455(4), b = 10.973(3), c = 13.512(4) Å, β = 92.83(2)°. Those of the nitroethylene derivative (RANET) are also monoclinic, C2/c, Z = 8, a = 27.901(9), b = 9.432(4), c = 13.795(5) Å, β = 93.96(3)°. Both structures were solved, using diffractometer data, by direct methods and refined by least-squares to R = 4.7% and 3.8%, respectively. The molecules of RANTS are linked together by pairs of S ⋯ H-N hydrogen bonds connecting two thiosemicarbazone moieties, while in RANET no intermolecular hydrogen bonding was found. The conformation of the two molecules is quite different. The RANTS molecule is folded as a 'pair of tongs' with a pivot at the sulphur atom of the sulphide linkage, but the two limbs are twisted in such a way that no relevant intramolecular interaction is possible. No such folding is present in RANET where the furan ring is oriented, with respect to the sulphide group, in a direction opposite to that found in RANTS.