(3S,4S)-3-((R)-(1-(tert-butyldimethylsilyl)oxy)ethyl)-4-((3R)-4-oxotetrahydro-4H-thiopyrane-3-yl)azetidine-2-one

(5R,6S)-6-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-7-oxo-3-(S)-tetrahydro-furan-2-yl-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid allyl ester

benzyl 7α-<(1R)-1-hydroxyethyl>-2-oxo-1-oxa-3-cephem-4-carboxylate

(3S,4R)-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[2-(trimethylsilyl)ethylseleno]-2-azetidinone

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