5-Acetyl-1,3-dimethylbarbituric Acid

Typical Procedure 1: Primary amino group selective protection using DAB
A solution of (1R,2R)-1,2-diphenylethanediamine (1.06 g, 5.0 mmol) and 1,3-dimethyl-5-acetylbarbituric acid (DAB) (1) (991 mg, 5 mmol) in anhydrous THF (15 mL) is stirred at room temperature under Ar. After stirring for 48 h, the reaction mixture is concentrated under reduced pressure, and the residue is purified by column chromatography using neutral silica gel (n-hexane:ethyl acetate=1:1) to afford the product 2 (1.92 g, 98% yield).

Typical Procedure 2: Primary amino group selective deprotection using DAB
A solution of 3 (196 mg, 0.396 mmol) and 2-aminoethanol (238 µL, 3.96 mmol) in anhydrous EtOH (3 mL) is stirred at 50 °C for 24 h under Ar. After removal of the solvent under reduced pressure, the residue is purified by column chromatography using neutral silica gel (n-hexane:ethyl acetate=1:1) to afford the product 4 (124 mg, 99% yield).