methyl 3-O-acetyl-6-O-benzyl-2-deoxy-2-dimethylmaleimido-β-D-glucopyranosyl-(1->4)-3,6-di-O-benzyl-2-deoxy-2-dimethylmaleimido-β-D-glucopyranosyl-(1->4)-3-O-acetyl-6-O-benzyl-2-deoxy-2-dimethylmaleimido-β-D-glucopyranoside