Triethyl phosphite → allyl (4R,5S,6S)-6-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-methyl-3-methylthio-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate

Participants

Reaction Steps

A mixture of triethyl phosphite (1.43 g), toluene (3 ml) and a mixture (1.0 g) of (3S,4S)-1-(allyloxyoxalyl)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1R)-1-{(methylthio)thiocarbonyl}ethyl]-2-oxoazetidine and (3S,4S)-1-(allyloxyoxalyl)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1S)-1-{(methylthio)thiocarbonyl}ethyl]-2-oxoazetidine was heated at 80° C. for 26 hours and then refluxed for 16 hours. After removal of the solvent, the residue was dissolved in hexane, washed with water, dried, and concentrated in vacuo. The oily residue was purified by silica gel column chromatography [diethyl ether-hexane (1:3, V/V)] to afford a mixture (118 mg) of allyl (4R,5S,6S)-6-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-methyl-3-methylthio-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate and allyl (4S,5S,6S)-6-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-methyl-3 -methylthio-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylate.

Provenance & Evidence