Methanol → N-[2-(4-Chloro-alpha-methylcinnamylamino)ethyl]-5-isoquinolinesulfonamide

7.30 g of N-(2-aminoethyl)-5-isoquinolinesulfonamide was dissolved in 150 ml of methanol, to the solution was added 6.30 g of p-chlorobenzalacetone, and the mixture was stirred at a room temperature for 36 hours. After addition of 1.32 g of sodium tetrahydrideborate with ice-water cooling, the mixture was stirred for 30 minutes. The reaction mixture was concentrated to half of original volume under a reduced pressure, and after adding 300 ml of ethyl acetate, washed three times with water. The aqueous layer was extracted with 100 ml of ethyl acetate, and the extract was washed with water as described above. The ethyl acetate layers were combined, washed twice with a saturated sodium chloride aqueous solution, dried over magnesium sulfate, filtered, and evaporated under a reduced pressure to remove the solvent. The resulting residue was purified using a silica gel column (silica gel: 200 g; eluant: 5% methanol in chloroform), to obtain 6.78 g of the title compound in a colorless amorphous form, while recovering the residual starting material.