[NH2:1][C@H:2]([C:6]([OH:8])=[O:7])[CH:3]([CH3:5])[CH3:4].C(=O)([O-])[O-].[Na+].[Na+].[C:15]([S:18][CH2:19][CH:20]([CH3:24])[C:21](Cl)=[O:22])(=[O:17])[CH3:16]>O>[C:15]([S:18][CH2:19][CH:20]([CH3:24])[C:21]([NH:1][C@H:2]([C:6]([OH:8])=[O:7])[CH:3]([CH3:5])[CH3:4])=[O:22])(=[O:17])[CH3:16]L-valine (88 g) and sodium carbonate (40 g) are dissolved in water (1 l.) and the solution is chilled in an ice bath with vigorous stirring. 3-Acetylthio-2-methylpropanoyl chloride (135 g) and a solution of sodium carbonate (120 g) in 500 ml of water are added in five equal portions over a 15 minute period. After 1.5 hours, the reaction mixture is extracted with ethyl acetate, the aqueous phase is acidified with concentrated hydrochloric acid and extracted with ethyl acetate. The organic phase is washed with water, dried over magnesium sulfate and concentrated to dryness to yield 190 g of N-(3-acetylthio-2-methylpropanoyl)-L-valine. The named product is obtained by following the procedure of Step (b), Example 49.
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