allyl (4S,8S,9R,10S)-4-[[1,2-bis(allyloxycarbonyl)guanidino]methyl]-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

allyl (4R,8S,9R,10S)-4-[(S)-(1-allyloxycarbonyl)pyrrolidin-3-ylthiomethyl]-10-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-11-oxo-1-azatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

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