Study of the structure of Droxicam, 5-methyl-3-(2-pyridyl)-2H,5H-1,3-oxazino[5,6-c][1,2]benzothiazine-2,4(3H)-dione 6,6-dioxide, using X-ray crystallography and 1H and 13C nuclear magnetic resonance spectroscopy

Abstract

The anti-inflammatory drug Droxicam, 5-methyl-3-(2-pyridyl)-2H,5H-1,3-oxazino[5,6-c]-[1,2]benzothiazine-2,4(3H)-dione 6,6-dioxide, has been investigated by n.m.r. spectroscopy, mass spectrometry, and X-ray crystallography. The ¹H and ¹³C n.m.r. spectra of this compound have been completely assigned. The single-crystal X-ray investigation, R= 0.0348 (R_w= 0.0374), showed the compound to be monoclinic, space group P2₁/c, a= 8.160(3), b= 15.698(3), c= 12.058(2), β= 98.09(2)°. The three-ring fused system showed an almost planar conformation distorted from coplanarity by the thiazine ring that exhibits a half-chair conformation. The pyridine ring is almost perpendicular to the oxazine ring.