An alternative synthesis of O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-L-α-aminobutanoyl-D-isoglutamine

Silver triflate-promoted condensation of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide ( VIII ) with benzyl 2-acetamido-6-O-benzoyl-2-deoxy-3-O-(methoxycarbonyl)-methyl-α-D-glucopyranoside ( IV ) afforded benzyl 2-acetamido-4-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-6-O-benzoyl-2-deoxy-3-O-(methoxycarbonyl)methyl-α-D-glucopyranoside ( IX ) which, after deprotection, was converted into the acid XI . Condensation of acid XI with L-α-aminobutanoyl-D-isoglutamine benzyl ester and subsequent hydrogenolysis of the product XIII furnished compound XIV . Benzyl 2-acetamido-6-O-benzoyl-2-deoxy-3-O-(methoxycarbonyl)methyl-α-D-glucopyranoside ( IV ) was prepared by partial benzoylation of benzyl 2-acetamido-2-deoxy-3-O-(methoxycarbonyl)methyl-α-D-glucopyranoside ( III ) with benzoyl cyanide.