Hydrochloric Acid → 6-Amino-5-[(6-hydroxy-2,5,7,8-tetramethyl-2-chromanylmethyl)amino]-3-methyl-1-phenyl-2,4 (1H, 3H)-pyrimidinedione

The compound of Example 14 (64 mg, 1.0 mmol) was dissolved in THF (10 mL). To the resultant solution was added borane-methyl sulfide complex (10 M, 0.24 mL, 2.4 mmol). The resultant reaction mixture was refluxed for 5 h. To the resultant was added 1N hydrochloric acid (2.4 mL) under ice-cooling. The resultant mixture was refluxed for 2 h, followed by concentration under reduced pressure. The residue was extracted with dichloromethane after addition of 1N aqueous solution of sodium hydroxide. The organic layer was washed with 10% aqueous solution of sodium chloride, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was crystallized by addition of ethyl acetate and ether to give the title compound (yield 35%).