[C:1]([O:5][C:6](=[O:21])[NH:7][C:8]1([C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[CH2:12][CH:11](O)[O:10][C:9]1=[O:14])([CH3:4])([CH3:3])[CH3:2].C([O-])(O)=O.[Na+].[NH2:27][C@H:28]([C:31]([O:33][CH3:34])=[O:32])[CH2:29][SH:30].Cl.O>CCO>[CH3:34][O:33][C:31]([CH:28]1[CH2:29][S:30][CH:11]([CH2:12][C:8]([NH:7][C:6]([O:5][C:1]([CH3:4])([CH3:3])[CH3:2])=[O:21])([C:9]([OH:10])=[O:14])[C:15]2[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=2)[NH:27]1)=[O:32]To a solution of compound 14 (5.6 g, 19.1 mmol) in EtOH (80 mL) was added 1 M aq. NaHCO3 solution (19.1 mL, 19.1 mmol), followed by the addition of L-Cys-OMe.HCl (3.3 g 19.1 mmol). The pH value of the resulting mixture was adjusted to 6.5 with 1 M NaHCO3 solution. After stirring overnight, the mixture was poured into water, extracted with ethyl acetate, and the combined organic phases were dried over Na2SO4 and concentrated to afford product 15 (7 g, 51.1%). MS (M+1): 411. This product was used in the next step without further purification.
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