Under a nitrogen atmosphere, 54 mg (0.308 mmol) of N-methoxycarbonyl-(L)-valine and 92 mg (0.308 mmol) of TPTU in 1 ml of DMF and 101 μl (0.91 mmol) of NMM are stirred at room temperature for 10 min. 190 mg (0.308 mmol) of 1-[4-(2-tert-butyl-2H-tetrazol-5-yl)-phenyl]-4(S)-hydroxy-5(S)-amino-2-N-[N-methoxycarbonyl-(L)-tert-leucyl]amino-6-phenyl-2-azahexane hydrochloride (Example 34g) in 2 ml of DMF are added thereto and the mixture is stirred at room temperature overnight to complete the reaction. The reaction mixture is diluted with methylene chloride and washed with brine. The aqueous phases are extracted 2× with methylene chloride; the organic phases are filtered through cotton wadding, concentrated by evaporation and chromatographed (SiO2; methylene chloride/methanol 30:1): TLC: Rf=0.21 (methylene chloride/methanol 19:1); FAB MS (M+H)+=738.
