To a mixture of N-methyl-N-{2-[5-methyl-5-(piperazine-1-ylmethyl)-4,5-dihydro-1,3-thiazol-2-yl]-1H-indol-7-yl}thiophene-2-sulfonamide (0.28 g), triethylamine (0.17 ml) and tetrahydrofuran (6 ml) was added methanesulfonyl chloride (0.06 ml) at 0° C., and the reaction mixture was stirred overnight at room temperature, and concentrated. The residue was subjected to basic silica gel column chromatography to give the title compound (0.26 g, yield 81%) as colorless crystals from a fraction eluted with ethyl acetate-hexane (4:1, volume ratio).
