Sodium hydride (0.075 g) was added to a solution of 1,2,3,9-tetrahydro-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one (0.7 g) in dimethylformamide (10 ml) and the mixture was stirred at room temperature for 30 min. Methyl chloroformate (0.3 ml) was added and stirring continued at room temperature for 4 h. The resulting solution was basified with sodium carbonate (100 ml) filtered, and the filtrate was extracted with ethyl acetate (2×50 ml). The combined organic extracts and solid were washed with water (3×50 ml), dried (Na2SO4) and evaporated in vacuo to give a solid. Purification by flash chromatography (A) gave a solid, which was dissolved in ethanol (5 ml) and added to a solution of maleic acid (0.018 g) in ethanol (5 ml) to give the title compound (0.07 g) m.p. 91°-92°.
