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, C
11H
11N
5,
D1, and diethyl 2,2′‐[({[amino(pyrazin‐2‐yl)methylidene]hydrazinylidene}methylidene)bis(sulfanediyl)]diacetate, C
14H
19N
5O
4S
2,
B1, maintain planarity due to conjugation and attractive intramolecular hydrogen‐bond contacts, while methyl 3‐[amino(pyrazin‐2‐yl)methylidene]‐2‐methyldithiocarbazate, C
8H
11N
5S
2,
C1, and benzyl 3‐[amino(pyrazin‐2‐yl)methylidene]‐2‐methyldithiocarbazate, C
14H
15N
5S
2,
C2, are not planar, due to methylation 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.
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