Complete tetraglycosylation of a calix[4]arene by a chemo-enzymatic approach.

Polyglycosylated calixarenes are efficient and selective multivalent ligands for lectins. However, the chemical decoration of these macrocyclic scaffolds with saccharides of increasing complexity is hampered by the highly complex chemistry of carbohydrates. An alternative to the conventional approach is the enzymatic diversification of simple glycocluster-presented glycans. In this work, we present a highly efficient chemo-enzymatic approach to tetra-N-acetyl-lactosaminylcalix[4]arene via glycan extension catalyzed by a human β-1,4-galactosyltransferase. This demonstrates that calixarenes can be exhaustively processed by enzymatic glycosyl transfer despite the heavy steric crowding, paving the way to the design and achievement of multivalent ligands based on these macrocyclic scaffolds having complex branched glycans.