100 mg (0.256 mmol) of (S)-α-amino-N-[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropyl-5-hexenyl]-imidazole-4-propionamide and 0.052 ml of Hunig base in 2 ml of acetonitrile were treated at room temperature with 100 mg of N-(dibenzylcarbamoyl)-3-phenyl-L-alanine and 113 mg of BOP and subsequently stirred at room temperature for 12 hours. Thereafter, the reaction solution was poured onto 1N hydrochloric acid/ice, extracted with ethyl acetate, the extracts were dried over sodium sulfate and the solvent was removed under reduced pressure. Chromatography of the residue on silica gel using a 10:1 mixture of methylene chloride and methanol as the eluting agent yielded 130 mg of 1,1-dibenzyl-3-[(S)-α-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropyl-5-hexenyl]carbamoyl]-2-imidazol-4-ylethyl]carbamoyl]phenethyl]urea in the form of an amorphous solid. MS: 761 (M+H)+.
