A mixture of 95 mg of (RS)-α-[(2-morpholinoethyl)carbamoylmethyl]-1-naphthalenepropionic acid, 100 mg of (S)-α-amino-N-[(1S,2S.4S)-1-(cyclohexylmethyl) 2-hydroxy-4-isopropyl-5-hexenyl]imidazole-4-propionamide and 97 mg of HBTU in acetonitrile was stirred at room temperature for 3.5 hours and then worked-up in the usual manner. The residue was chromatographed on silica gel with a 4: mixture of methylene chloride and methanol as the eluting agent, to obtain 60 mg of N-[(1S,2S.4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropyl-5-hexenyl]-α-[3-[(2-morpholinoethyl)carbamoyl]-2-(1-naphthylmethyl)propionamido]imidazole-4-propionamide as a foam. MS: 743 (M+H)+.
