Complex oligosaccharides containing α-d-xylosyl-(1→6)-β-d-glucosyl residues and unsubstituted β-(1→4)-linked d-glucosyl units were readily synthesized using enzymatic coupling catalyzed by the Cel7B E197A glycosynthase from Humicola insolens. Constituting this library required four key steps: (1) preparing unprotected building blocks by chemical synthesis or enzymatic degradation of xyloglucan polymers;