Reaction SMILES: [NH2:1][C@H:2]([C:7]([NH:9][CH2:10][C:11]([NH:13][C@H:14]([C:16]([NH:18][C@H:19]([C:29]([NH:31][C@H:32]([C:41]([NH:43][C@H:44]([C:54]([NH:56][C@H:57]([C:60]([NH:62][C@H:63]([C:65]([O:67][C:68]([CH3:71])([CH3:70])[CH3:69])=[O:66])[CH3:64])=[O:61])[CH2:58][OH:59])=[O:55])[CH2:45][CH2:46][C:47](=[O:53])[O:48][C:49]([CH3:52])([CH3:51])[CH3:50])=[O:42])[CH2:33][C:34](=[O:40])[O:35][C:36]([CH3:39])([CH3:38])[CH3:37])=[O:30])[CH2:20][CH2:21][C:22](=[O:28])[O:23][C:24]([CH3:27])([CH3:26])[CH3:25])=[O:17])[CH3:15])=[O:12])=[O:8])[CH2:3][C:4](=[O:6])[NH2:5].[NH:72]([C:193]([O:195][CH2:196][C:197]1[CH:202]=[CH:201][CH:200]=[CH:199][CH:198]=1)=[O:194])[C@H:73]([C:86]([NH:88][C@H:89]([C:102]([NH:104][C@H:105]([C:116]([NH:118][C@H:119]([C:130]([N:132]1[CH2:192][CH2:191][CH2:190][C@H:133]1[C:134]([NH:136][C@H:137]([C:141]([NH:143][C@H:144]([C:157]([NH:159][C@H:160]([C:164]([NH:166][C@H:167]([C:180]([N:182]1[CH2:189][CH2:188][CH2:187][C@H:183]1[C:184](O)=[O:185])=[O:181])[CH2:168][C:169]1[CH:174]=[CH:173][C:172]([O:175][C:176]([CH3:179])([CH3:178])[CH3:177])=[CH:171][CH:170]=1)=[O:165])[CH:161]([CH3:163])[CH3:162])=[O:158])[CH2:145][CH2:146][CH2:147][CH2:148][NH:149][C:150]([O:152][C:153]([CH3:156])([CH3:155])[CH3:154])=[O:151])=[O:142])[CH:138]([CH3:140])[CH3:139])=[O:135])=[O:131])[CH2:120][CH2:121][CH2:122][NH:123][C:124](=[NH:129])[NH:125][N+:126]([O-:128])=[O:127])=[O:117])[CH2:106][CH2:107][CH2:108][NH:109][C:110](=[NH:115])[NH:111][N+:112]([O-:114])=[O:113])=[O:103])[CH2:90][CH2:91][CH2:92][CH2:93][NH:94][C:95]([O:97][C:98]([CH3:101])([CH3:100])[CH3:99])=[O:96])=[O:87])[CH2:74][CH2:75][CH2:76][CH2:77][NH:78][C:79]([O:81][C:82]([CH3:85])([CH3:84])[CH3:83])=[O:80]>CN(C=O)C>[NH:72]([C:193]([O:195][CH2:196][C:197]1[CH:198]=[CH:199][CH:200]=[CH:201][CH:202]=1)=[O:194])[C@H:73]([C:86]([NH:88][C@H:89]([C:102]([NH:104][C@H:105]([C:116]([NH:118][C@H:119]([C:130]([N:132]1[CH2:192][CH2:191][CH2:190][C@H:133]1[C:134]([NH:136][C@H:137]([C:141]([NH:143][C@H:144]([C:157]([NH:159][C@H:160]([C:164]([NH:166][C@H:167]([C:180]([N:182]1[CH2:189][CH2:188][CH2:187][C@H:183]1[C:184]([NH:1][C@H:2]([C:7]([NH:9][CH2:10][C:11]([NH:13][C@H:14]([C:16]([NH:18][C@H:19]([C:29]([NH:31][C@H:32]([C:41]([NH:43][C@H:44]([C:54]([NH:56][C@H:57]([C:60]([NH:62][C@H:63]([C:65]([O:67][C:68]([CH3:69])([CH3:70])[CH3:71])=[O:66])[CH3:64])=[O:61])[CH2:58][OH:59])=[O:55])[CH2:45][CH2:46][C:47](=[O:53])[O:48][C:49]([CH3:50])([CH3:51])[CH3:52])=[O:42])[CH2:33][C:34](=[O:40])[O:35][C:36]([CH3:37])([CH3:38])[CH3:39])=[O:30])[CH2:20][CH2:21][C:22](=[O:28])[O:23][C:24]([CH3:25])([CH3:26])[CH3:27])=[O:17])[CH3:15])=[O:12])=[O:8])[CH2:3][C:4](=[O:6])[NH2:5])=[O:185])=[O:181])[CH2:168][C:169]1[CH:174]=[CH:173][C:172]([O:175][C:176]([CH3:178])([CH3:179])[CH3:177])=[CH:171][CH:170]=1)=[O:165])[CH:161]([CH3:162])[CH3:163])=[O:158])[CH2:145][CH2:146][CH2:147][CH2:148][NH:149][C:150]([O:152][C:153]([CH3:154])([CH3:156])[CH3:155])=[O:151])=[O:142])[CH:138]([CH3:140])[CH3:139])=[O:135])=[O:131])[CH2:120][CH2:121][CH2:122][NH:123][C:124](=[NH:129])[NH:125][N+:126]([O-:128])=[O:127])=[O:117])[CH2:106][CH2:107][CH2:108][NH:109][C:110](=[NH:115])[NH:111][N+:112]([O-:114])=[O:113])=[O:103])[CH2:90][CH2:91][CH2:92][CH2:93][NH:94][C:95]([O:97][C:98]([CH3:99])([CH3:100])[CH3:101])=[O:96])=[O:87])[CH2:74][CH2:75][CH2:76][CH2:77][NH:78][C:79]([O:81][C:82]([CH3:85])([CH3:83])[CH3:84])=[O:80]
Reactant: CC(C)[C@H](NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)[C@@H](NC(=O)[C@@H]1CCCN1C(=O)[C@H](CCCNC(=N)N[N+](=O)[O-])NC(=O)[C@H](CCCNC(=N)N[N+](=O)[O-])NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)OCc1ccccc1)C(C)C)C(=O)N[C@@H](Cc1ccc(OC(C)(C)C)cc1)C(=O)N1CCC[C@H]1C(=O)O
Reactant: C[C@H](NC(=O)CNC(=O)[C@@H](N)CC(N)=O)C(=O)N[C@@H](CCC(=O)OC(C)(C)C)C(=O)N[C@@H](CC(=O)OC(C)(C)C)C(=O)N[C@@H](CCC(=O)OC(C)(C)C)C(=O)N[C@@H](CO)C(=O)N[C@@H](C)C(=O)OC(C)(C)C
Solvent: CN(C)C=O
Product: CC(C)[C@H](NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)[C@@H](NC(=O)[C@@H]1CCCN1C(=O)[C@H](CCCNC(=N)N[N+](=O)[O-])NC(=O)[C@H](CCCNC(=N)N[N+](=O)[O-])NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)[C@H](CCCCNC(=O)OC(C)(C)C)NC(=O)OCc1ccccc1)C(C)C)C(=O)N[C@@H](Cc1ccc(OC(C)(C)C)cc1)C(=O)N1CCC[C@H]1C(=O)N[C@@H](CC(N)=O)C(=O)NCC(=O)N[C@@H](C)C(=O)N[C@@H](CCC(=O)OC(C)(C)C)C(=O)N[C@@H](CC(=O)OC(C)(C)C)C(=O)N[C@@H](CCC(=O)OC(C)(C)C)C(=O)N[C@@H](CO)C(=O)N[C@@H](C)C(=O)OC(C)(C)C
Temperature: 0 °C
Reaction time: 0.25 h
Yield: 85.1 %

Procedure:
3.0 g. (2.95 mmoles) of H-25-32-OtBu and 5.46 g. (2.95 mmoles) of Z-Lys(BOC)-Lys(BOC)-Arg(NO2)-Arg(NO2)-Pro-Val-Lys(BOC)-Val-Tyr(tBu)-Pro-OH (Brit. Pat. No. 1 201 053) are dissolved in 33 ml. of DMF. The solution is cooled to 0°C, and 3.35 g. (4.42 mmoles) of DCC-PFPOH complex are added to it. The reaction mixture is kept at 0°C for 15 minutes, thereafter at room temperature for 6 hours. The separated DCU is filtered off, and the filtrate is passed into 450 ml. of dry ether. The separated crude product is filtered off and purified by precipitation from methanol with ether. 7.18 g. (85.1 %) of Z-15-32-OtBu are obtained. Rf3 = 0.35; [α]D = -26.4° (c = 0.42, in DMF).