A synthetic disaccharide with a GlcAβ1-4GlcNAc linkage, the unsulfated, N-acetylated disaccharide repeat of the heparan sulfate (HS) / heparin backbone. As a model fragment of the HS/heparin precursor (N-acetylheparosan) it is a useful probe and reference standard for studies of HS/heparin biosynthesis, sulfotransferase activity, and lectin/protein-binding research. Heparan sulfate (HS) and heparin are sulfated glycosaminoglycans found as components of proteoglycans. HS, in close proximity to cell surfaces and extracellular matrix proteins, plays essential physiological roles binding hundreds of proteins, and may play a role in SARS-CoV-2 infection through virus binding to ACE2; heparin is mainly found in mast cell secretory granules. Synthetic, structurally defined HS/heparin fragments are valuable probes for sulfation-pattern-dependent protein binding, anticoagulant and growth-factor signaling research, and as standards for analytical and structure-activity studies.