Water → (1R,4S)-1-butyrylamino-4-(hydroxymethyl)-2-cyclopentene

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Reaction Conditions

Reaction Steps

34.7 g of (1R,4S)-1-amino-4-hydroxymethyl-2-cyclopentene hydrochloride and 2 g of 4-N,N-dimethylaminopyridine were dissolved in 600 ml of methylene chloride. The solution was cooled to 0° C. Then 52 g of triethylamine were added dropwise (5 min). The mixture was stirred for a further 30 min. A solution of 35.2 g of butyryl chloride in 60 ml of methylene chloride was metered into the mixture at 0C over the course of 1 h. The mixture was stirred for a further 1.5 h at between 0 and 20° C., and then 600 ml of water were added. After phase separation, the aqueous phase was extracted with 600 ml of methylene chloride. The combined organic phases were washed 3 times with 500 ml of 10% strength NaOH each time, and then completely evaporated. The dried solid was dissolved in 120 ml of methanol. The solution was mixed with 5 g of K2CO3 and stirred for a further 2 h at room temperature. The inorganic salts were filtered off and washed with 20 ml of methanol. The filtrate was neutralized with 2N HCl. The suspension was filtered and the filter cake was washed with 20 ml of methanol. The filtrate was completely evaporated. The solid residue was dried and crystallized in 150 ml of toluene. 28.5 g of title compound were obtained. The yield was 67%.

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