8-Methoxycarbonyloctyl-2-deoxy-2-phthalimido-3-O-benzyl-4-O-(3',4',6'-tri-O-acetyl-2'-deoxy-2'-phthalimido-b-D-glucopyranosyl)-b-D-glucopyranoside (8-Methoxycarbonyloctyl-3-O-benzyl-2,2'-dideoxy-2,2'-diphthalimido-3'.4'.6'-L-O-acetyl-b-cellobiose)