To a methanol (8 ml) solution of 2-amino-5-chloro-α-(4-tert-butoxycarbonylaminomethylphenyl)benzyl alcohol (0.83 g) were added trimethyl acetaldehyde (220 mg) and acetic acid (170 mg). The mixture was stirred for 10 minutes at room temperature, to which was added sodium cyano borohydride (160 mg). The mixture was stirred overnight at room temperature, to which was added acetic acid ethyl ester (100 ml). The mixture was washed with water and dried over anhydrous Na2SO4. 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-(4-tert-butoxycarbonylaminomethylphenyl)-2-neopentylaminobenzyl alcohol (0.99 g) as a colorless oily product.
