[NH2:1][C@H:2]([CH2:6][C:7]#[CH:8])[C:3]([OH:5])=[O:4].C([O-])([O-])=O.[Na+].[Na+].O.[Cl:16][C:17]1[CH:18]=[C:19]([S:24](Cl)(=[O:26])=[O:25])[CH:20]=[CH:21][C:22]=1[Cl:23].Cl.[Na+].[Cl-]>O.O1CCOCC1.CCOC(C)=O>[Cl:16][C:17]1[CH:18]=[C:19]([S:24]([NH:1][C@H:2]([CH2:6][C:7]#[CH:8])[C:3]([OH:5])=[O:4])(=[O:25])=[O:26])[CH:20]=[CH:21][C:22]=1[Cl:23](R)-2-Aminopent-4-ynoic acid (16.0 g, 141 mmol) and Na2CO3.H2O (36.8 g, 296 mmol) were dissolved in 500 mL H2O and 300 mL p-dioxane. To this solution was added 3,4-dichlorobenzene-1-sulfonyl chloride (33.0 g, 134 mmol) dropwise over 25 min. The solution was stirred at RT for 19 h. The solution was then acidified with 5N HCl to pH 1. EtOAc (400 mL) and sat'd NaCl aq. (200 mL) were added and organic layer was separated. The aqueous phase was extracted with EtOAc (200 mL×2), and the combined EtOAc extracts were washed with brine (400 mL×4) and dried over Na2SO4. The solvent was removed under reduced pressure and dried in vacuo to yield 38.
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