Hydrochloric Acid → {6-(Ethoxycarbonyl)-2-[3-(4-methoxyphenyl)propyl]-3-oxo-2,3-dihydro-4H-1,4-benzothiazin-4-yl}acetic acid

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Reaction Steps

Under ice-cooling, a boron trifluoride-diethyl ether complex (26.6 ml) was added dropwise to a solution of ethyl 4-(2-tert-butoxy-2-oxoethyl)-2-[3-(4-methoxyphenyl)propyl]-3-oxo-3,4-dihydro-2H-1,4-benzothiazine-6-carboxylate (13.16 g) and dimethyl sulfide (26.3 ml) in dichloromethane (250 ml). The resulting mixture was slowly warmed up to room temperature and then stirred overnight. The mixture was poured into a 1N aqueous hydrochloric acid solution and extracted with chloroform. The oil layer was washed twice with a 1N aqueous hydrochloric acid solution, dehydrated over anhydrous sodium sulfate and then concentrated under reduced pressure. {6-(Ethoxycarbonyl)-2-[3-(4-methoxyphenyl)propyl]-3-oxo-2,3-dihydro-4H-1,4-benzothiazin-4-yl}acetic acid (10.64 g) was obtained as a yellow oil.

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