To a methanol (4 ml) solution of 2-amino-5-chloro-α-(3-tert-butoxycarbonylaminophenyl) benzyl alcohol (0.4 g) were added trimethyl acetaldehyde (109 mg) and acetic acid (76 mg). The mixture was stirred for 10 minutes at room temperature, to which was added sodium cyano borohydride (79 mg). The mixture was stirred for one hour at room temperature, to which was added acetic acid ethyl ester (50 ml). The mixture was washed with water and dried over anhydrous MgSO4. The solvent was then distilled off, and the residue was purified by means of a silica gel column chromatography to give the object 5-chloro-α-(3-tert-butoxycarbonylaminophenyl)-2-neopentylaminobenzyl alcohol (0.43 g) as a colorless amorphous solid product.
