Cyclohexyl isocyanate → 1-Cyclohexyl-3-(5-ethoxy-2,2-dioxido-1,2,3-benzoxathiazin-4-yl)urea

0.15 g (0.61 mmol) of 4-amino-5-ethoxy-1,2,3-benzoxathiazine 2,2-dioxide is stirred with 0.1 g (0.79 mmol) of cyclohexyl isocyanate in 30 ml of dry tetrahydrofuran in the presence of 10 mg of DBU, first at room temperature for 1 hour and then at 40° C. for 18 hours. The mixture is concentrated under reduced pressure, and the residue is dissolved in dichloromethane and washed with water. The organic phase is dried over magnesium sulphate and concentrated under reduced pressure. This gives 0.15 g of crude product which, after dissolution in 14 ml of acetonitrile and 6 ml of water, is purified by means of reversed phase HPLC (Kromasil 100 C18, 250×40 mm, 5 μm, 0.01% HCOOH/H2O acetonitrile gradient 34/66, isocratic). This gives 55 mg (24.2% of theory) of compound I-24 as a white solid.