2,2-Dimethoxypropane → (6S,7S)-8-oxo-2,2-dimethyl-5-methylidene-7-(1-(R)-benzyloxycarbonyloxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane

Participants

Reaction Steps

A solution of (3S,4S)-4-(1-hydroxymethylethenyl)-3-(1-(R)-benzyloxycarbonyloxyethyl)-2-azetidinone (3.7 g) and 2,2-dimethoxypropane (1.45 g) in dry dichloromethane (26 ml) was treated with boron trifluoride-etherate (0.14 ml) at room temperature for 1.5 hours. The reaction mixture was washed successively with saturated sodium bicarbonate (15 and water (20 ml×2), and dried over anhydrous sodium sulfate. Filtration and concentration of the filtrate in vacuo gave an oily residue, which was purified by silica gel chromatography to yield (6S,7S)-8-oxo-2,2-dimethyl-5-methylidene-7-(1-(R)-benzyloxycarbonyloxyethyl)-3-oxa-1-azabicyclo[4.2.0]octane.

Provenance & Evidence