To a suspension of 6.20 g (10.5 mmols) of N-benzyloxycarbonyl-β-benzyl-L-aspartyl-D-valine (R)-α-methoxymethylbenzylamide in 200 ml of methanol and 50 ml of water was added 1.50 g of 10% Pd-carbon (water content 50%). The mixture was reduced under hydrogen under heat at 40° C. The catalyst was removed by filtration, and the resulting filtrate was concentrated under reduced pressure to 15 ml. The crystal thus precipitated was removed by filtration and dried to obtain 2.69 g (7.36 mmols, 70.0% ) of α-L-aspartyl-D-valine (R)-α-methoxymethylbenzylamide.
