Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Chemistry and Pharmacology
The title compounds, (2S)-N-[5-(4-chlorophenyl)-2,3-dihydro-6H-1,3,4-thiadiazin-2-ylidene]-2-[(phenylsulfonyl)amino]propanamide, C18H17ClN4O3S2, (I), (2R)-N-[5-(4-fluorophenyl)-6H-1,3,4-thiadiazin-2-yl]-2-[(phenylsulfonyl)amino]propanamide, C18H17FN4O3S2, (II), and (2S)-N-[5-(5-chloro-2-thienyl)-6H-1,3,4-thiadiazin-2-yl]-2-[(phenylsulfonyl)amino]propanamide, C16H15ClN4O3S3, (III), are potent inhibitors of matrix metalloproteinases. In all three compounds, the thiadiazine ring adopts a screw-boat conformation. The molecules of compound (I) show a short intramolecular NAla—H...Nexo hydrogen bond [N...N 2.661 (3) Å] and are linked into a chain along the c axis by Nendo—H...Sendo and Nendo—H...OAla hydrogen bonds [N...S 3.236 (3) and N...O 3.375 (3) Å] between neighbouring molecules. In compound (II), the molecules are connected antiparallel into a chain along the a axis by Nexo—H...OAla and NAla—H...Nendo hydrogen bonds [N...O 2.907 (6) and N...N 2.911 (6) Å]. The molecules of compound (III) are dimerized antiparallel through Nexo—H...Nendo hydrogen bonds [N...N 2.956 (7) and 2.983 (7) Å]. The different hydrogen-bonding patterns can be explained by an amido–imino tautomerism (prototropic shift) shown by different bond lengths within the 6H-1,3,4-thiadiazine moiety.
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