CC(OC([NH:8][C@H:9]([C:20]([OH:22])=O)[CH2:10][CH2:11][CH2:12][N:13]=[C:14]([NH:16][N+:17]([O-:19])=[O:18])[NH2:15])=O)(C)C.[Cl:23][C:24](OCC(C)C)=O.CN1CCOCC1.[ClH:38].C(O)C>O1CCCC1>[NH2:8][C@H:9]([C:20]([CH2:24][Cl:23])=[O:22])[CH2:10][CH2:11][CH2:12][NH:13][C:14](=[NH:15])[NH:16][N+:17]([O-:19])=[O:18].[ClH:38]Boc Arg(NO2)OH (5.0 g, 15.6 mmol) was dissolved in 60 ml of tetrahydrofuran (THF) and was allowed to react with isobutyl chloroformate (2.06 ml, 15.6 mmol) in the presence of N-methylmorpholine (1.72 ml, 15.6 mmol) for 10 min at -20° C. The mixed anhydride preparation was filtered, and the filtrate was added to 120 ml of ethereal diazomethane. After stirring the reaction solution for 30 min at 0° C., 80 ml of ether was added. The product crystallized from the reaction solution in the cold. The Boc-Arg(HO2)CHNH2 product was dissolved in a minimum volume of THF and was allowed to react with ethanol HCl (20 mmol) at room temperature until nitrogen evolution ceased.
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