the carbon skeleton being further substituted by doubly-bound oxygen atoms

Full Title

Compounds containing amino and carboxyl groups bound to the same carbon skeleton > having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton > with amino and carboxyl groups bound to carbon atoms of the same non-condensed six-membered aromatic ring > the carbon skeleton being further substituted by doubly-bound oxygen atoms