[C:1]([NH:11][CH2:12][C:13]([OH:15])=O)([O:3][CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1)=[O:2].CN1CCOCC1.ClC(OCC(C)C)=O.Cl.[NH2:32][CH2:33][C@H:34]([NH:40][S:41]([C:44]1[CH:49]=[CH:48][CH:47]=[CH:46][CH:45]=1)(=[O:43])=[O:42])[C:35]([O:37][CH2:38][CH3:39])=[O:36]>CCOC(C)=O>[CH2:38]([O:37][C:35](=[O:36])[C@@H:34]([NH:40][S:41]([C:44]1[CH:49]=[CH:48][CH:47]=[CH:46][CH:45]=1)(=[O:42])=[O:43])[CH2:33][NH:32][C:13](=[O:15])[CH2:12][NH:11][C:1]([O:3][CH2:4][C:5]1[CH:6]=[CH:7][CH:8]=[CH:9][CH:10]=1)=[O:2])[CH3:39]N—Cbz-glycine (339 mg, 1.62 mmol) was dissolved in 8 mL EtOAc, cooled to −15° C., then NMM (196 μL, 1.8 mmol) and isobutyl chloroformate (230 μL, 1.8 mmol) were added. After 20 min, the mixed anhydride solution was added to amine 3-4 (0.50 mg, 1.6 mmol) suspended in 5 mL EtOAc and the reaction was warmed to RT for 90 min. Following dilution with EtOAc, the mixture was washed with water, sat. NaHCO3, 5% KHSO4, and brine, dried (MgSO4), filtered and concentrated. Flash chromatography (silica, 75% EtOAc/hexane) provided amide 3-5 as a colorless oil.
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