Methanesulfonic Acid → benzyl (S)-1-((1S,2R,4R)-2-acetamido-4-(isopropyl(methyl)amino)cyclohexyl)-2-oxopyrrolidin-3-ylcarbamate

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Reaction Conditions

Reaction Steps

Example 1, Alternative Preparation, Step 5: The tert-Butyl carbamate 9 (50 g) was dissolved in Toluene (500 mL) and i-PrOH (150 mL). The resulting solution was then heated to 60° C. Methanesulfonic acid (19.6 mL) was added below 65° C. Upon reaction completion (HPLC), the mixture was cooled to RT and triethylamine (69.4 mL) added slowly below 25° C. Acetic anhydride was then added below 25° C. After 1 h acetic acid (250 mL) was added below 25° C. The toluene phase was discarded and 2-methyl-THF (500 mL) was added to the aqueous phase. The mixture was stirred vigorously and basified with NaOH (25% aqueous solution) to pH 12. The aqueous phase was discarded and the organic layer was washed with brine (250 mL). The organic layer was concentrated under reduced pressure and continuously replaced with i-PrOH. The solution was cooled and filtered to provide benzyl {(S)-1-[(1S,2R,4R)-2-acetylamino-4-(isopropyl-methyl-amino)-cyclohexyl]-2-oxo-pyrrolidin-3-yl}-carbamate 10 in i-PrOH solution which was used directly in the hydrogenation.

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