To a mixture of N-[2-(benzylthio)-2-methyl-3-oxopropyl]-7-[methyl(2-thienylsulfonyl)amino]-1H-indole-2-carboxamide (0.40 g), morpholine (0.13 ml) and 1,2-dichloroethane (4 ml) was added sodium triacetoxyborohydride (0.36 g) at 0° C., and the mixture was stirred at room temperature for 4 hr. Saturated aqueous sodium hydrogencarbonate was added to the reaction mixture, 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 basic silica gel column chromatography to give the title compound (0.25 g, yield 55%) as colorless crystals from a fraction eluted with ethyl acetate-hexane (2:1, volume ratio). melting point 150-152° C.
