To a solution of tert-butyl N-[(1S)-1-[4-[[[(2-aminophenyl)amino]carbonyl]amino]benzyl]-2-hydroxyethyl]-N-[(2S)-2-hydroxy-3-phenoxypropyl]carbamate (20.0 mg) in 1,2-dichloroethane (200 μl) were added successively 1.0 M solution of pyridine in 1,2-dichloroethane (54.5 μl) and 1.0 M solution of methanesulfonyl chloride in 1,2-dichloroethane (43.6 μl) at room temperature. After stirring for 2 hours, the solvent was removed by evaporation and the residue was purified by a recycling preparative high pressure liquid chromatography equipped with a gel permeation chromatography column (eluent: chloroform) to give a light brown solid. The solid was dissolved in 1,2-dichloroethane (200 μl). To the solution was added trifluoroacetic acid (200 μl) and the mixture was stirred for 30 minutes. The solvent was removed by evaporation to give N-[2-[[[[4-[(2S)-3-hydroxy-2-[[(2S)-2-hydroxy-3-phenoxypropyl]amino]propyl]phenyl]amino]-carbonyl]amino]phenyl]methanesulfonamide trifluoroacetate (20.3 mg) as a light brown solid.
