Cl.N1[CH2:9][CH2:8][CH2:7][C@H:3]1[C:4]([NH2:6])=O.C(N[C@H](C(O)=O)CC1N=CNC=1)[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1.[C:28](#[N:30])C.[CH2:31](N[C@H](C(N1CCC[C@H]1C(N)=O)=O)CC1N=CNC=1)C1C=CC=CC=1>C(N(CC)CC)C>[CH:11]1([N:30]=[C:28]=[N:6][CH:4]2[CH2:3][CH2:7][CH2:8][CH2:9][CH2:31]2)[CH2:12][CH2:13][CH2:14][CH2:15][CH2:16]1Prolinamide hydrochloride (6 g.) and N-t-butyloxycarbonyl-Nim -benzylhistidine (13.8 g.) were reacted in 200 ml. acetonitrile in the presence of 4.04 g. triethylamine and 10.3 g N,N'-dicyclohexylcarbodiimide to give N-t-butyloxycarbonyl-Nim -benzyl-histidyl-prolinamide as an oily residue. The oil was dissolved in 150 ml. of 2N hydrobromic acid solution in glacial acetic acid. The solution was kept at room temperature for 1 hour in a stoppered flask and then poured into 1500 ml. anhydrous ether. The solid precipitate was redissolved in methanol and precipitated again with ether to give 13.2 g (65.6%) of crystalline Nim -benzyl-histidyl-prolinamide dihydrobromide melting at 196- 8°C after recrystallization from methanol-ether.
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