A solution of 1,1-dimethylethyl (1-{2-hydroxy-3-[7-(methyloxy)-2-oxo-3,4-dihydro-1,8-naphthyridin-1(2H)-yl]propyl}-4-piperidinyl)carbamate (301 mg, 0.694 mmol) in chloroform (10 ml) and triethylamine (0.24 ml, 1.735 mmol) at rt under argon was treated with methanesulfonic anhydride (242 mg, 1.388 mmol) and heated at reflux for 2 h. The reaction mixture was then evaporated and dissolved in acetonitrile (10 ml), treated with sodium iodide (520 mg, 3.47 mmol) and heated at 80° C. for 0.25 h. The mixture was then cooled, evaporated was then treated with water (200 ml), extracted with 20% methanol/DCM (3×200 ml). The organic extracts were dried (MgSO4), evaporated and chromatographed (0-10% methanol/DCM) to give the product as an orange oil (194 mg, 70%).
