Synonyms: 1-Azetidinesulfonic acid, 2-methyl-4-oxo-3-(((phenylmethoxy)carbonyl)amino)-, ion(1-), trans-, N,N,N-tributyl-1-butanaminium;1-Butanaminium, N,N,N-tributyl-, salt with trans-2-methyl-4-oxo-3-(((phenylmethoxy)carbonyl)amino)-1-azetidinesulfonic acid (1:1);Tetrabutylammonio, salt with trans-3-((benzyloxycarbonyl)amino)-2-methyl-4-oxoazetidine-1-sulphonic acid (1:1)