2-(2-methoxycarbonylethylthio)ethyl 2,3,6-tri-O-acetyl-4-O-<2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl)-β-D-galactopyranosyl>-β-D-glucopyranoside