(3S,4S)-3-<(tert-butyldimethylsiloxy)methyl>-4-<1(R)-carboxyethyl>azetidin-3-one

(3S,4R)-3-(hydroxymethyl)-4-<1(R)-methyl-3-diazo-3-<(allyloxy)carbonyl>-2-oxopropyl>azetidin-2-one

(3S,4R)-3-<(tert-butyldimethylsiloxy)methyl>-4-<1(R)-methyl-3-<(allyloxy)carbonyl>-2-oxopropyl>azetidin-2-one

allyl (4R,5S,6S)-6-(hydroxymethyl)-4-methyl-7-oxo-3-<(pyridin-3-ylmethyl)thio>-1-azabicyclo<3.2.0>hept-2-ene-2-carboxylate