Chemists have devised a synthetic process to make gram-scale amounts of heparin-related oligosaccharides, a development with potential to improve the quality and safety of blood thinners and make available other heparin oligosaccharide medicines. Heparin and heparan sulfate are a family of glycosaminoglycans that play a role in regulating blood-vessel growth, blood coagulation, and the spread of cancer tumors. The clinically used drugs are short-chain oligosaccharides currently isolated from slaughtered pigs and cattle, but chemists would like to make them synthetically for better quality control. Unlike proteins or nucleic acids, however, glycosaminoglycan biosynthesis is not template driven, making it tricky to synthesize from scratch. One limitation has been an affordable synthesis of a uronic acid disaccharide building block. Earlier this year, John M. Gardiner and coworkers at the University of Manchester, in England, overcame that problem with a multi-gram-scale synthesis of an iduronate thioglycoside (J. Org. Chem., DOI: 10.1021/jo300722y). Gardiner’s team has now used this disaccharide in an iterative process to prepare the first gram amounts of a structurally well-defined longer-chain heparin dodecasaccharide (Org. Lett., DOI: 10.1021/ol303112y). The Manchester researchers envision using their modular approach as a general strategy to prepare heparins of different lengths and sulfation patterns on a scale suitable for clinical use, including for cancer.