To a solution of (S)-3-(4-(benzyloxy)phenyl)-2-(2-(3-(3-benzylureido)propanoyl)-1-methylhydrazinyl)propanoic acid (Compound VII-1) 126 mg (0.25 mmol) in dichloromethane 1.5 ml, 2,2-diethoxy-N-(naphthalen-1-ylmethyl)ethanamine (Compound IV-2) 85 mg (0.31 mmol) and DMT-MM 173 mg (0.63 mmol) were added and the mixture was stirred at room temperature for 3 hr. The reaction mixture was diluted with chloroform 50 ml and washed with water 50 ml twice and brine 50 ml twice and dried over magnesium sulfate and filtered. The mother solution was concentrated in vacuo and the residue was purified on silica gel column chromatography (Merck 60N spherical, neutral 10 ml elution by chloroform:methanol=100:0 to 90:10, each elution 50 ml) to give the desired product as pale yellow oil 85.0 mg (35.8%).
