Abstract: A process for the preparation of a monomer compound containing a structural unit of the formula ##STR1## wherein one of Q and Q' are independently the group --NH--CO--OR.sup.IV or hydrogen and the other --NH--CO--COOR.sup.V or hydrogen, a urethane or an isocyanate, wherein R.sup.IV and R.sup.V aliphatic or carbocyclic hydrocarbon groups being substituted or unsubstituted group; R and R'" are unsubstituted or monosubstituted aromatic radicals (wherein at least one oxamidic ester and) wherein at least one oxamidic acid ester with the grouping --NH--CO--CO--OR.sup.V, wherein R.sup.V is as defined, is reacted with an isocyanate or an isocyanate forming compound at temperatures of -20.degree. to +280.degree. C in the presence or absence of a catalyst,A compound of said formula and a shaped article containing said compound.