Hydrochloric Acid → methyl (2S)-2-amino-3-{4-[(2,6-dichlorobenzoyl)amino]phenyl}propionate hydrochloride

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The solid (S)-2-tert-butoxycarbonylamino-3-[4-(2,6-dichlorobenzoylamino)phenyl]propionic acid methyl ester (43.45 g, 92.97 mmol) in dioxane (90 mL) was treated with 166 mL of 4.0N hydrochloric acid in dioxane at room temperature. After 5 minutes, the solids went into solution and the mixture was stirred for 2 h. Then, some of the dioxane was removed under vacuum to afford a yellow syrup and 250 mL of ethyl ether was added. A gum was formed which was dissolved in THF (100 mL) and methanol (100 mL). The solvent was removed under vacuum to obtain 43.7 g (100% yield) of (S)-2-amino-3-[4-(2,6-dichlorobenzoylamino)phenyl]propionic acid methyl ester hydrochloride salt as a white solid: mp 180-195° C. This was stored in the refrigerator under argon atmosphere. ES(+)-HRMS m/e calcd. for C17H16Cl2N2O3 (M+H)+ 367.0616, obsd. 367.0611.

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