allyl (4S,8S,9R,10S)-4-(N,N-bis(allyloxycarbonyl)aminomethyl)-10-[(R)-1-hydroxyethyl]-11-oxo-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (4S,8S,9R,10S)-10-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-triethylsilyloxymethyl-11-oxo-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (4S,8S,9R,10S)-4-(N,N-bis(allyloxycarbonyl)aminomethyl)-10-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-11-oxo-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

{(2R,3S)-3-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-2-[(1R,3R)-3-(tert-butyl-dimethyl-silanyloxymethyl)-2-oxo-cyclohexyl]-4-oxo-azetidin-1-yl}-oxo-acetic acid allyl ester

diallyl imidodicarbonate

allyl (4S,8S,9R,10S)-10-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-t-butyldimethylsilyloxymethyl-11-oxo-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (4S,8S,9R,10S)-10-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-hydroxymethyl-11-oxo-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

(3S,4R)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-[(2'R,6'R)-2'-hydroxymethylcyclohexanone-6'-yl]azetidin-2-one