A new class of synthetic glycosulfopeptides (GSPs) which have one or more sulfated tyrosine residues and a glycan linked to the peptide, the glycan preferably including a sialyl Lewis.sup.x group or a sialyl Lewis.sup.a group. In a preferred version the GSPs have an O-glycan comprising a .beta.1,6 linkage to a GalNAc. The present invention further contemplates in vitro methods of the synthesis of these GSPs without the use of the cells and methods of their use in vivo as powerful anti-inflammatory antithrombotic, or anti-metastatic compounds. The invention also contemplates a method of synthesizing oligosaccharides by cleaving the glycan from the GSP.