Hydrochloric Acid → Ethyl (1S,3R,4R)-3-[[(1,1-dimethylethoxy)carbonyl]amino]-4-[(methylsulfonyl)oxy]cyclohexanecarboxylate

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Reaction Steps

Ethyl (1S,3R,4R)-3-(tert-butoxycarbonylamino)-4-hydroxycyclohexane-1-carboxylate (53.5 g) and triethylamine (130 ml) were dissolved in dichloromethane (500 ml), and methanesulfonyl chloride (42 ml) was added dropwise while cooling the solution to −10° C. to −15° C. After stirring for 20 minutes at the same temperature, the mixture was heated to room temperature over 30 minutes and further stirred for 2 hours. The reaction mixture was cooled to 0° C., 0.5N hydrochloric acid (800 ml) was added dropwise, and the mixture was extracted with dichloromethane. The resultant organic layer was washed with a saturated aqueous solution of sodium hydrogencarbonate and saturated saline and dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure to obtain crude ethyl (1S,3R,4R)-3-(tert-butoxycarbonylamino)-4-(methane-sulfonyloxy)cyclohexane-1-carboxylate.

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