To a mixture of 4-oxo-N-[2-(1,3-thiazol-2-yl)-1H-indol-7-yl]-4-(2-thienyl)butanamide (1.43 g), tetrahydrofuran (10 ml) and methanol (10 ml) was added sodium borohydride (0.16 g) at 0° C., and the mixture was stirred at the same temperature for 1 hr. To the reaction mixture was added 10% aqueous citric acid solution, and the mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with saturated brine, dried (MgSO4) and concentrated. The residue was subjected to silica gel column chromatography and the title compound (1.21 g, yield 84%) was obtained as colorless crystals from a fraction eluted with ethyl acetate. melting point 155-157° C.
