To 1.5 mL of a methanol solution containing 280 mg of tert-butyl(2,3-dihydro-1,4-benzodioxin-6-ylmethyl)(1-(2-(5-amino-2-oxoquinolin-1(2H)-yl)ethyl)piperidin-4-yl)carbamate, 0.5 mL of water, 83 mg of sodium carbonate and 99 mg of dimethyl sulfate were added, and stirred at room temperature for 3 days. The insoluble material was filtered off, and the solvent was removed under reduced pressure, and purified by silica gel column chromatography [Silica Gel; Fuji Silysia Chemical Ltd., Chromatorex-NH, eluent; ethyl acetate:methanol=10:1], to give 65 mg of tert-butyl(2,3-dihydro-1,4-benzodioxin-6-ylmethyl)(1-(2-(5-(N-methylamino)-2-oxoquinolin-1(2H)-yl)ethyl)piperidin-4-yl)carbamate as a yellow oil.
