Dry THF (150 ml) was cooled to −65° C. in a dry ice-acetone bath under an argon atmosphere and n-butyl lithium hexane solution (1.6M: 45.2 ml) was added. A solution of 6-bromo-N-methyl-2-naphthamide (8.68 g) in dry THF (700 ml) cooled to 10° C. was added to this solution at not more than −55° C., and the mixture was stirred for 1 h. A dry THF solution (60 ml) of 5,6-dihydro-7H-pyrrolo[1,2-c]imidazol-7-one (3.65 g) was added dropwise. The mixture was stirred at the same temperature for 1.5 h and saturated aqueous ammonium chloride solution (120 ml) was added to stop the reaction. The solvent was evaporated under reduced pressure and an ethanol-soluble material was extracted from the resulting residue and the solvent was evaporated again. The residue was purified by flash silica gel column chromatography (eluent, chloroform/methanol containing ammonia (7%), 19/1→9/1). The eluate was recrystallized from methanol to give the title compound (3.36 g) as colorless crystals.
