A solution of 7-[methyl(2-thienylsulfonyl)amino]-1H-indole-2-carbothioamide (0.50 g), ethyl but-2-ynoate (0.40 mL) and tributylphosphine (0.40 mL) in a mixed solvent of tetrahydrofuran (16 mL)-toluene (8 mL) was stirred at 50° C. for 3 hr. The reaction solution was concentrated under reduced pressure, and the obtained residue was subjected to silica gel column chromatography (ethyl acetate:hexane=1:4-1:1) to give the title compound (0.33 g, yield: 50%) as a pale-yellow oil. A part of the oil was crystallized from ethyl acetate-hexane to give pale-yellow crystals. MS: 464 (MH+). melting point 101-102° C.
