To 20 ml of dimethylformamide add potassium carbonate (0.01044 mol) and then 6-benzoylbenzothiazolinone (0.00453 mol). Heat at 100° C. for 1 hour. Add the compound obtained in Step B of Example 1 (0.00348 mol) and heat at 150° C. for 16 hours. Evaporate off the dimethylformamide. Take up the residue in 50 ml of water and then extract with 50 ml of dichloromethane twice. The organic phase is dried over MgSO4 and then evaporated. The residue is recrystallised form methanol and yields the title compound in the form of a solid.
