N-Ethylpiperidine → (3s,4r)-3-[(1r)-1-(Tert-butyldimethylsilyloxy)ethyl]-4-[(1r)-1-methyl-2-[7-dimethoxymethyl(pyridin-3-yl)imidazo[5,1-b]thiazol-2-yl]-2-oxoethyl]azetidin-2-one

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反応手順

Methylene chloride (2 ml) was added to 0.69 g of tin(II) trifluoromethanesulfonate under an argon atmosphere, and the mixture was cooled to −20° C. A solution of 0.25 g of 2-propionyl-7-(pyridin-3-yl)dimethoxymethylimidazo[5,1-b]thiazole in 1.5 ml of methylene chloride and 0.12 ml of N-ethylpiperidine were added thereto, and the mixture was stirred for 2 hr. A solution of 0.14 g of (3S,4R)-4-acetoxy-3-[(1R)-1-tert-butyldimethylsilyloxyethyl]azetidin-2-one in 1 ml of methylene chloride was added at 0° C., and the mixture was stirred at room temperature for one hr. A saturated aqueous sodium bicarbonate solution was added to the reaction mixture to stop the reaction, and the reaction mixture was extracted with ethyl acetate. The organic layer was washed with a 5% aqueous sodium bicarbonate solution and a 20% aqueous sodium chloride solution in that order and was dried over anhydrous magnesium sulfate. The solvent was removed by evaporation, and the residue was analyzed by HPLC (Cosmosil 5C18-MS, 4.6×150 mm, a 70% aqueous acetonitrile solution). As a result, it was found that the yield of (3S,4R)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1R)-1-methyl-2-[7-dimethoxy(pyridin-3-yl)methylimidazo[5,1-b]thiazol-2-yl]-2-oxoethyl]azetidin-2-one was 45 mg. The results of analysis by NMR were in agreement with the results of analysis in Example 18.

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