t-butyl (S)-2-[[(S)-α-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropyl-5-hexenyl]carbamoyl]-2-imidazol-4-ylethyl]carbamoyl]phenethyl]acetyl]-1-pyrrolidinecarboxylate 、 t-butyl (S)-2-[[(R)-alpha-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropyl-5-hexenyl]carbamoyl]-2-imidazol-4-ylethyl]carbamoyl]phenethyl]acetyl]-1-pyrrolidinecarboxylate 以there was obtained t-butyl (S)-2-[[(S)-α-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropylhexyl]carbamoyl]-2-imidazol-4-ylethyl]-carbamoyl]phenethyl]acetyl]-1-pyrrolidinecarboxylate (less polar isomer) and t-butyl (S)-2-[[(R)-α-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropylhexyl]carbamoyl]-2-imidazol-4-ylethyl]carbamoyl]phenethyl]-acetyl]-1-pyrrolidinecarboxylate的产率得到t-butyl (S)-2-[[(S)-α-[[(S)-1-[[(1S,2S,4S)-1-(cyclohexylmethyl)-2-hydroxy-4-isopropylhexyl]carbamoyl]-2-imidazol-4-ylethyl]-carbamoyl]phenethyl]acetyl]-1-pyrrolidinecarboxylate