Hydrochloric Acid → HCID 57236660, compound

Participants

Reaction Steps

To a solution of (2S)-1-(N-allyloxycarbonyl-N-methylamino)-2-(allyloxycarbonylaminomethyl)butan-3-one (14.59 g) in dichloromethane (110 ml) were added N-ethylpiperidine (13.5 ml) and trimethylsilyl trifluoromethanesulfonate (18.9 ml) at -10° C. and the resulting mixture was stirred at ambient temperature for 1 hour. To a solution of (3R,4R)-4-acetoxy-3-[(1R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone (21.1 g) in dichloromethane (140 ml) were added N-ethylpiperidine (10.1 ml) and trimethylsilyl trifluoromethanesulfonate (14.2 ml) at -20° C. and the mixture was stirred at 0° C. for 1 hour. To a mixture of the latter solution and zinc bromide (44.05 g) was added the former solution at 0° C. and the resulting mixture was allowed to stir at ambient temperature for 2 hours. The reaction mixture was diluted with a mixture of water (800 ml) and ethyl acetate (800 ml). After adjusting pH to 0.7 with hydrochloric acid (6N), the mixture was allowed to stir at ambient temperature for 2 hours. The separated organic layer was washed in turn with water and brine. After adjusting pH to 7 with aqueous sodium hydrogen carbonate, the organic layer was washed with brine, dried over magnesium sulfate. Evaporation of the solvent gave a residue which was chromatographed on silica gel (1.5 l) eluting with a mixture of n-hexane and ethyl acetate (9:1-2:8, V/V) to give (3S,4R)-4-[(3S)-4-(N-allyloxycarbonyl-N-methylamino)-3-(allyloxycarbonylaminomethyl)-2-oxobutyl]-3-[(1R)-1-t-butyldimethylsilyloxyethyl]-2-oxoazetidine (19.42 g).

Provenance & Evidence