Ethyl Acetate → 3-(1,2,3,4,10,14b-Hexahydrodibenzo[c,f]pyrazino[1,2,a]azepin-2-yl)propyl carbamate

0.2 ml of trichloroacetyl isocyanate were added to a solution of 400 mg of 3-(1,2,3,4,10,14b-hexahydrodibenzo[c,f]pyrazino[1,2-a]azepin-2-yl)propanol (prepared as described in Example 16) in 20 ml of methylene chloride, whilst ice-cooling, and the mixture was stirred at room temperature for 2 hours. At the end of this time, the solvent was removed by distillation under reduced pressure. The resulting residue was dissolved in 22 ml of methanol, 9.0 g of silica gel were added to the solution and the mixture was stirred at room temperature for 15 hours. At the end of this time, the mixture was filtered using a Celite (trade mark) filter aid, and the filtrate was concentrated by evaporation under reduced pressure. The residue was subjected to column chromatography through silica gel eluted with ethyl acetate, to give, after recrystallization from ethyl acetate, 260 mg (yield 59%) of the title compound as crystals, melting at 160°-161° C.