[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[OH:10])([O-:3])=[O:2].C(O[C@@H](CCN[C:38]([O:40][CH2:41][C:42]1[CH:47]=[CH:46][CH:45]=[CH:44][CH:43]=1)=[O:39])C(=O)OC1C(F)=C(F)C(F)=C(F)C=1F)(=O)C1C=CC=CC=1.CCN(C(C)C)C(C)C>CN(C=O)C>[C:38]([O:10][C:5]1[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=1[N+:1]([O-:3])=[O:2])([O:40][CH2:41][C:42]1[CH:47]=[CH:46][CH:45]=[CH:44][CH:43]=1)=[O:39]To a stirring solution of 3′,4′,3′″,4′″-tetra-dehydro-3,2′,6′,2′″,6′″-penta-Cbz-neomycin (4, 190 mg, 0.156 mmol) in DMF (2 mL) was added succinimidyl benzoyloxy(2-Cbz-aminoethyl)carbamate (3, 81 mg, 0.18 mmol) and the reaction was stirred under a nitrogen atmosphere. DIPEA (67 μL, 0.38 mmol) was added and the reaction was stirred for 2 days. The reaction mixture was purified on a 2-inch reverse-phase HPLC column, followed by treatment with sat. aq. NaHCO3 to remove the benzoyl protecting group to yield a crude, which was purified on a 1-inch reverse-phase column to yield (5) (60 mg, 0.041 mmol, 26.3% yield): MS m/z (M+Na)+ calc. 1475.5, obs. 1475.4.
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