p. 291 - 297
(2007/10/02)6,6-dibromopenicillanic acid
(pivaloyloxy)methyl 6α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-1-oxopenicillanate
(pivaloyloxy)methyl 7α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>-3-methylceph-3-em-4-carboxylate
(pivaloyloxy)methyl 6α-<1(R)-<<<(p-nitrobenzyl)oxy>carbonyl>oxy>ethyl>penicillanate
(pivaloyloxy)methyl 6α-bromo-6β-<1(R)-hydroxyethyl>penicillanate