Zur Differenzierung der antennenspezifischen enzymatischen Galaktosylierung durch kernmagnetische Resonanzspektroskopie

Differentiation of the Branch‐Specific Enzymic Galactosylation by Nuclear‐Magnetic Resonance Spectroscopy A spacer‐modified biantennary trisaccharide glycoside ( 2 ) carrying two GlcNAc end groups was galactosylated by UDP‐Gal and β‐(1→4)‐ D ‐galactosyltransferase to yield compounds 3a, 3b and 4 . The non‐separable monogalactosylated compounds 3a and 3b were investigated by NMR spectroscopy (COSY, COLOC, RELAY) to determine a potential branch‐specific transgalactosylation found for native acceptor‐oligosaccharides ( 1 ). Since the “3‐branch” is galactosylated at the same rate as the “6‐branch” the presence not only of the center‐mannosyl unit but also of the flanking mannosyl residues replaced by spacers in compound 2 are necessary for site specificity.