Trimethylsilyl triflate → (3S,4R)-4-[(E)-4-{(2S)-1-allyloxycarbonylpyrrolidin-2-yl}-3-methyl-2-oxo-3-butenyl]-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-2-oxoazetidine

Participants

Reaction Conditions

Reaction Steps

To a solution of (2S)-1-allyloxycarbonyl-2-(2-methyl-3-oxo-1-butenyl)pyrrolidine (9.00 g) and triethylamine (6.3 ml) in dichloromethane (200 ml) was added trimethylsilyl trifluoromethanesulfonate (11.7 ml) at -20° C. After stirring at 0° C. for 1 hour, a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-2-azetidinone (10.9 g) and zinc bromide (11.9 g) in ethyl acetate (70 ml) was added to the mixture and the resultant mixture was stirred at 0° C. for 45 minutes. The reaction mixture was taken up into a mixture of ethyl acetate (600 ml) and water (600 ml). After adjusting pH to 4 with aqueous sodium hydrogen carbonate, the organic layer was separated, washed with brine, dried over magnesium sulfate and evaporated. The residue was chromatographed on silica gel (400 ml) eluting with a mixture of n-hexane and ethyl acetate (9:1-5:5 V/V) to give (3S, 4R)-4-[(E)-4-{(2S)-1-allyloxycarbonylpyrrolidin-2-yl}-3-methyl-2-oxo-3-butenyl]-3[(1R)-1-t-butyldimethylsilyloxyethyl]-2-oxoazetidine (9.96 g).

Provenance & Evidence