Synthesis of Methyl O -(2-Acetamido-2-Deoxy-α-D-Glucopyranosyl)-(1→2)- O -α-D-Glucopyranosyl-(l→2)-α-D-Galactopyranoside and of Methyl O -α-D-Glucopyranosyl-(l→2)- O -α-D-Galactopyranosyl-(1→3)-O-[α-D-Galactopyranosyl-(1→6)]-α-D-Glucopyranoside, Corresponding to Parts of the Outer Core of the Salmonella Cell Wall Lipopolysaccharide