A method of making a synthetic glycopeptide, by addition of a synthetic oligosaccharide oxazoline to a GlcNAc-containing peptide precursor in the presence of an enzyme selected from among Endo-A and Endo-M. In a specific implementation, the method is utilized to synthesize a trivalent V3-domain glycopeptide including three V3-domain glycopeptides on a scaffold, wherein the three V3-domain glycopeptides are arranged to mimic the V3 domain presentation in trimeric gp120. Such trivalent V3-domain glycopeptides can be utilized in a vaccine for the treatment or prevention of HIV-1 infection.