[CH:1]12[CH:6]([C:7](OCC)=[O:8])[CH:5]1[CH2:4][N:3]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:2]2.[Li+].[OH-].CC[N:23](C(C)C)C(C)C.C(Cl)CCl.C1C=CC2N(O)N=NC=2C=1.[NH4+].[Cl-]>C1COCC1.CO.O.CN(C=O)C>[C:7]([CH:6]1[CH:5]2[CH:1]1[CH2:2][N:3]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:4]2)(=[O:8])[NH2:23]
To a solution of 1 (6.65 g, 26.2 mmol) in THF (100 mL) and MeOH (40 mL) was added a solution of LiOH (4.40 g, 104 mmol) in H2O (40 mL) and stirred for 2 h. The reaction was quenched upon addition of 0.5 N HCl (150 mL) and extracted with EtOAc (2×200 ml). The combined organic extracts were dried over MgSO4 and concentrated under vacuum to afford the intermediate acid. Dissolved in DMF (90 mL), added DIPEA (18.8 mL, 104 mmol), EDC (5.84 g, 31.4 mmol), HOBt (4.24 g, 31.4 mmol) and NH4Cl (4.16 g, 78.5 mmol). The reaction was sealed and stirred for 48 h. Diluted the reaction with water (350 mL) and extracted with EtOAc (2×250 mL). The combined organic extracts were washed with water (2×300 mL), brine (300 mL), dried over MgSO4 and concentrated under vacuum to afford 2 (1.84 g, 31%) as a white solid; 1H-nmr (400 MHz, CDCl3) δ 5.75 (s, 1H), 5.45 (s, 1H), 3.68 (d, J=7.0 Hz, 1H), 3.58 (d, J=11.0 Hz, 1H), 3.43 (d, J=11.0 Hz, 2H), 2.07 (s, 2H), 1.44 (s, 9H), 1.31-1.26 (m, 1H); LC-MS (214 nM) 2.15 min (>98%), m/z 171 [M-tBu].
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