allyl (8S,9R,10S)-5-[[1-(allyloxycarbonyl)pyrrolidin-3-yl]carbamoyl]-10-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-11-oxo-1,5-diazatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (8S,9R,10S)-5-methyl-10-[(R)-1-hydroxyethyl]-11-oxo-1,5-diazatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (8S,9R,10S)-5-acetyl-10-[(R)-1-hydroxyethyl]-11-oxo-1,5-diazatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

allyl (8S,9R,10S)-10-[(R)-1-hydroxyethyl]-11-oxo-5-(N-methyl)thiocarbamoyl-1,5-diazatricyclo[7.2.0.03,8]undec-2-ene-2-carboxylate

(3R,4S)-4-[(R)-1-(tert-butoxycarbonyl)-3-oxopiperidin-4-yl]-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-2-azetidinone