Boron trifluoride etherate → (3S,4S)-4-(1-(R)-hydroxymethylethyl)-3-(1-(R)-benzyloxycarbonyloxyethyl)-2-azetidinone

Participants

Reaction Steps

To a solution of (3S,4R)-4-(1-(R)-t-butyldimethylsilyloxymethylethyl)-3-(1-(R)-benzyloxycarbonyloxyethyl)-1-di(p-anisyl)methyl-2-azetidinone (20 g) in dry dichloromethane (200 ml), there were added 1,3-dimethoxybenzene (7.8 g) and boron trifluoride etherate (23 g) at 10°-20° C., and the resultant mixture was stirred at room temperature for 3 hours, followed by heating under reflux for 3-5 hours. The reaction mixture was cooled down to 10°-15° C., washed successively with brine (200 ml×2), 2.5% aqueous sodium bicarbonate solution (200 ml) and brine (200 ml) and dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated in vacuo to give an oily residue, which was purified by silica gel chromatography to yield (3S,4S)-4-(1-(R)-hydroxymethylethyl)-3-(1-(R)-benzyloxycarbonyloxyethyl)-2-azetidinone.

Provenance & Evidence