Planarity of heteroaryldithiocarbazic acid derivatives showing tuberculostatic activity. II. Crystal structures of 3-[amino(pyrazin-2-yl) methylidene]-2-methylcarbazic acid esters

Abstract

Four compounds showing moderate antituberculostatic activity have been studied to test the hypothesis that the planarity of the 2-[amino(pyrazin-2-yl) methylidene]dithiocarbazate fragment is crucial for activity. N′-Anilinopyrazine-2-carboximidamide, C11H11N 5, D1, and diethyl 2,2′-[({[amino(pyrazin-2-yl)methylidene] hydrazinylidene}methylidene)bis-(sulfanediyl)]diacetate, C14H 19N5O4S2, B1, maintain planarity due to conjugation and attractive intramolecular hydrogenbond contacts, while methyl 3-[amino(pyrazin-2-yl)methylidene]-2-methyldithiocarbazate, C 8H11N5S2, C1, and benzyl 3-[amino(pyrazin-2-yl)methylidene]-2-methyldithiocarbazate, C14H 15N5S2, C2, are not planar, due to methyl-ation at one of the N atoms of the central N - N bond. The resulting twists of the two molecular halves (parts) of C1 and C2 are indicated by torsion angles of 116.5 (2) and -135.9 (2)°, respectively, compared with values of about 180° in the crystal structures of nonsubstituted compounds. As the methylated derivatives show similar activity against Mycobacterium tuberculosis to that of the nonsubstituted derivatives, maintaining planarity does not seem to be a prerequisite for activity. © 2011 International Union of Crystallography.