Natural-abundance 13C-NMR spectroscopy of two glyco-asparagines derived from the core of N-glycosidic carbohydrate chains

13C-NMR spectroscopic studies were carried out on Manalpha(1->6)Man beta(1->4)GlcNAc beta(1->4)GlcNAc beta(1->N)-Asn and Man alpha(1->6)Man beta(1->4)GlcNAc beta(1->4)[Fuc alpha(1->6)]GlcNAc beta(1->N)Asn, which are part of the invariant core of N-glycosidically linked carbohydrates of glycoproteins. All resonances of proton-bearing carbon atoms were unambiguously assigned. Where possible, the assignments were confirmed by selective proton-decoupling experiments