The structure of degradation compounds of T-1220 in aqueous solution was investigated. It was confirmed that in alkaline solution, α-{3-[2-(N-ethyl-N-oxaloamino) ethyl]-ureido} benzylpenicillin (T-1220 A), α-(4-ethyl-2, 3-dioxo-1-piperazinecarboxamido) benzylpenicilloic acid (T-1220B) and α-{3-[2-(N-ethyl-N-oxaloamino) ethyl] ureido} benzylpenicilloic acid (T-1220 C) were produced, and that in acid solution, T-1220 B and α-(4-ethyl-2, 3-dioxo-1-piperazinecarboxamido) benzylpenilloic acid (T-1220 D) wera produced.
