Disclosed herein is a process for the preparation of 2-(cyclohexylmethyl)-N-{ 2-[(2S)-1-methylpyrrolidin-2-yl]ethyl} -1,2,3,4-tetrahydroisoquinoline-7-sulfonamide, the process comprising a) reductively aminating 1,2,3,4-tetrahydroisoquinoline, or a salt thereof, with cyclohexanecarboxaldehyde to give 2-cyclohexylmethyl-1,2,3,4-tetrahydroisoquinoline, or a salt thereof； b) reacting 2-cyclohexylmethyl-1,2,3,4-tetrahydroisoquinoline, or a salt thereof, with excess chlorosulfonic acid to give 2-cyclohexylmethyl-1,2,3,4-tetrahydroisoquinoline-7-sulfonyl chloride HX salt, and optionally recrystallizing the 2-cyclohexylmethyl-1 ,2,3,4-tetrahydroisoquinoline-7-sulfonyl chloride HX salt； c) coupling 2-cyclohexylmethyl-1 ,2,3,4-tetrahydroisoquinoline-7 -sulfonyl chloride HX salt with (-)-2-(2-aminoethyl)-1-methylpyrrolidine to form 2-(cyclohexylmethyl)-N-{ 2-[(2S)-1-methylpyrrolidin-2-yl]ethyl} -1,2,3,4-tetrahydroisoquinoline-7-sulfonamide； d) optionally reacting 2-( cyclohexylmethyl)-N-{ 2-[(2S)-1-methylpyrrolidin-2-yl]ethyl} -1,2,3,4-tetrahydroisoquinoline-7-sulfonamide with a stoichiometric amount or an excess of a salt-forming acid in a solvent to form a salt or a hydrate or solvate thereof； and e) optionally recrystallizing the product of step d).
