Dimethylformamide → (2S,4R)-4-methanesulfonyloxy-1-(4-nitrobenzyloxycarbonyl)-2-{4,5,6,7-tetrahydropyrazolo [1,5-a]pyrimidin-4-yl)carbonylpyrrolidine

Participants

Reaction Conditions

Reaction Steps

To a mixture of N,N-dimethylformamide (1.20 ml) and tetrahydrofuran (2.4 ml) was added dropwise phosphorus oxychloride (1.25 ml) at -20° C. and the mixture was stirred at 5° C. for 5 minutes. To the mixture was added a solution of (2S,4R)-4-methanesulfonyloxy-1-(4-nitrobenzyloxycarbonyl)proline (4.0 g) in tetrahydrofuran (10 ml) under ice-cooling. The mixture was stirred at the same temperature for 30 minutes. To a solution of 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine (1.40 g) in tetrahydrofuran (20 ml) and water (10 ml) was added dropwise the solution obtained above with stirring under ice-cooling, keeping the pH to 8-10 with triethylamine. The mixture was stirred at the same condition for 1 hour. To the reaction mixture was added ethyl acetate (100 ml) and the organic layer was washed with saturated aqueous sodium hydrogen carbonate and saturated aqueous sodium chloride successively, dried over anhydrous magnesium sulfate and evaporated in vacuo. The resulting residue was chromatographed on silica gel (100 g) eluting with a mixture of chloroform and methanol (19:1, V/V). The fractions containing the desired compound were collected and evaporated in vacuo to give (2S,4R)-4-methanesulfonyloxy-1-(4-nitrobenzyloxycarbonyl)-2-{4,5,6,7-tetrahydropyrazolo [1,5-a]pyrimidin-4-yl)carbonylpyrrolidine (3.84 g).

Provenance & Evidence