Reaction SMILES: [C:1]([O:5][C:6]([N:8]1[CH2:15][CH2:14][CH:13]([CH:16]([CH3:18])[CH3:17])[C@H:9]1[C:10]([OH:12])=O)=[O:7])([CH3:4])([CH3:3])[CH3:2].[Cl:19][C:20]1[CH:21]=[CH:22][C:23]([N:35]2[CH:39]=[N:38][N:37]=[N:36]2)=[C:24]([CH:34]=1)[CH2:25][NH:26][C:27](=[O:33])[C@@H:28]1[CH2:32][CH2:31][CH2:30][NH:29]1.C(Cl)CCl.C1C=NC2N(O)N=NC=2C=1>CN(C=O)C.CC#N.O>[C:1]([O:5][C:6]([N:8]1[CH2:15][CH2:14][CH:13]([CH:16]([CH3:18])[CH3:17])[C@H:9]1[C:10]([N:29]1[CH2:30][CH2:31][CH2:32][C@H:28]1[C:27]([NH:26][CH2:25][C:24]1[CH:34]=[C:20]([Cl:19])[CH:21]=[CH:22][C:23]=1[N:35]1[CH:39]=[N:38][N:37]=[N:36]1)=[O:33])=[O:12])=[O:7])([CH3:2])([CH3:3])[CH3:4]
Reactant: O=C(NCc1cc(Cl)ccc1-n1cnnn1)[C@@H]1CCCN1
Reactant: CC(C)C1CCN(C(=O)OC(C)(C)C)[C@@H]1C(=O)O
Agent: On1nnc2cccnc21
Solvent: O
Solvent: CN(C)C=O
Solvent: ClCCCl
Product: CC(C)C1CCN(C(=O)OC(C)(C)C)[C@@H]1C(=O)N1CCC[C@H]1C(=O)NCc1cc(Cl)ccc1-n1cnnn1
Reaction time: 1 h

Procedure:
1-(tert-Butoxycarbonyl)-3-isopropylprolyl-N-[5-chloro-2-(1H-tetraazol-1-yl)benzyl]-L-prolinamide was prepared from 1-(tert-butoxycarbonyl)-3-isopropylproline (from the previous step, 252 mg, 0.98 mmol), N-[5-chloro-2-(1H-tetraazol-1-yl)benzyl]-L-prolinamide (Example 26, Step B, 300 mg, 0.98 mmol, 1.0 equiv), EDC (282 mg, 1.47 mmol, 1.5 equiv) and HOAt (67 mg, 0.49 mmol, 0.5 equiv) in DMF (1 mL) essentially according to the procedure described in Example 39, Step D. Reverse phase chromatography [95:5 water (+0.1% TFA)/CH3CN (+0.1% TFA) to 5:95 water (+0.1% TFA)/CH3CN (+0.1% TFA)] afforded the four separate diastereomers as clear oils. Each diastereomer was then dissolved in 2:1 CH2Cl2/TFA (3 mL) and stirred for 1 h. All reactions were concentrated to oils. Purification of each by reverse phase chromatography [95:5 water (+0.1% TFA)/CH3CN (+0.1% TFA) to 50:50 water (+0.1% TFA)/CH3CN (+0.1% TFA)] afforded the diastereomers as clear oils. Diastereomer A (most polar): 1H NMR (400 MHz, CD3OD): δ 9.54 (s, 1 H), 7.76 (d, J=2.0 Hz, 1 H), 7.55 (dd, J=2.0, 8.4 Hz, 1 H), 7.49 (d, J=8.4 Hz, 1 H), 4.49 (d, J=4.0 Hz, 1 H), 4.44–4.40 (m, 1 H), 4.33 (d, J=16.0 Hz, 1 H), 4.15 (d, J=15.6 Hz, 1 H), 3.80–3.75 (m, 1 H), 3.61–3.49 (m, 2 H), 3.41–3.35 (m, 1 H), 2.44–2.38 (m, 1 H), 2.30–2.22 (m, 1 H), 2.13–2.09 (m, 1 H), 2.04–1.93 (m, 3 H), 1.91–1.82 (m, 1 H), 1.81–1.73 (m, 1 H), 1.06 (d, J=6.8 Hz, 3 H), 1.01 (d, J=6.4 Hz, 3 H). HRMS (APCI) M+H: calculated for (C21H28N7O2Cl)+ 446.2066, found 446.2055. Diastereomer B: 1H NMR (400 MHz, CD3OD): δ 9.57 (s, 1 H), 8.61 (t, J=5.6 Hz, 1 H), 7.78 (d, J=2.4 Hz, 1 H), 7.54 (dd, J=2.4, 8.4 Hz, 1 H), 7.49 (d, J=8.4 Hz, 1 H), 4.60 (d, J=8.4 Hz, 1 H), 4.45–4.41 (m, 1 H), 4.32 (dd, J=6.0, 16.0 Hz, 1 H), 4.11 (dd, J=5.2, 16.0 Hz, 1 H), 3.81–3.77 (m, 1 H), 3.62–3.50 (m, 2 H), 3.36–3.30 (m, 1 H), 2.48–2.45 (m, 1 H), 2.26–2.11 (m, 4 H), 2.01–1.87 (m, 3 H), 0.97 (d, J=6.4 Hz, 3 H), 0.81 (d, J=6.4 Hz, 3 H). HRMS (APCI) M+H: calculated for (C21H28N7O2Cl)+ 446.2066, found 446.2057. Diastereomer C: 1H NMR (400 MHz, CD3OD): δ 9.53 (s, 1 H), 7.73 (d, J=2.4 Hz, 1 H), 7.57 (dd, J=2.4, 8.4 Hz, 1 H), 7.50 (d, J=8.4 Hz, 1 H), 4.37–4.34 (m, 2 H), 4.31 (d, J=15.6 Hz, 1 H), 4.19 (d, 16.0 Hz, 1 H), 3.80–3.76 (m, 1 H), 3.62–3.56 (m, 1 H), 3.48–3.43 (m, 1 H), 3.41–3.34 (m, 2 H), 2.37–2.34 (m, 1 H), 2.24–2.19 (m, 1 H), 2.12–1.88 (m, 4 H), 1.79–1.73 (m, 1 H), 1.02 (dd, J=6.8, 8.4 Hz, 6 H). HRMS (APCI) M+H: calculated for (C21H28N7O2Cl)+ 446.2066, found 446.2053. Diastereomer D (least polar): 1H NMR (400 MHz, CD3OD): δ 9.53 (s, 1 H), 7.76 (d, J=2.0 Hz, 1 H), 7.56 (dd, J=2.4, 8.4 Hz, 1 H), 7.50 (d, J=8.4 Hz, 1 H), 4.56 (d, J=7.6 Hz, 1 H), 4.36–4.31 (m, 2 H), 4.18 (d, J=15.6 Hz, 1 H), 3.80–3.76 (m, 1 H), 3.64–3.58 (m, 1 H), 3.53–3.48 (m, 1 H), 3.33–3.28 (m, 2 H), 2.53–2.49 (m, 1 H), 2.52–2.17 (m, 2 H), 2.13–2.06 (m, 1 H), 2.02–1.89 (m, 2 H), 1.74–1.69 (m, 1 H), 0.96 (d, J=6.8 Hz, 3 H), 0.95 (d, J=6.8 Hz, 3 H). HRMS (APCI) M+H: calculated for (C21H28N7O2Cl)+ 446.2066, found 446.2054.