(pivaloyloxy)methyl 7α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-3-methyl-1β-oxoceph-3-em-4-carboxylate
(5R,6R,7S)-3-Methyl-7-[(R)-1-(4-nitro-benzyloxycarbonyloxy)-ethyl]-5,8-dioxo-5λ4-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 2,2-dimethyl-propionyloxymethyl ester
(pivaloyloxy)methyl 7α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-2-diazo-3-methyl-1β-oxoceph-3-em-4-carboxylate
(pivaloyloxy)methyl 6α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-1-oxopenicillanate
(pivaloyloxy)methyl 6α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-1-hydroxy-2-methylcarbapen-2-em-3-carboxylate