Saccharides play due to their wide variability of conformational alternatives a crucial role in many recognition events including pathogen-cell adhesion and recognition, signaling, inflammatory response and others1. They are ordinarily found as glycoconjugates which are often localized on the cell surface or in the extracellular space. They are synthesized by glycosyltransferases in a process called glycosylation – one of the most common and imporatant enzymatic reaction in nature. This project is focused on human N-acetylglucosaminyltransferases, which add N acetylglucosaminyl residues to substrate. These glycosylation events accompany many physiological and pathological cell processes2. The upregulation of these enzymes may lead to an aberrant glycosylation and pathological modifications. Increased amounts of Lewis X and sialyl Lewis X is typical for cancer cells and the interaction between tumor-associated sialyl Lewis X and the endothelial cells of target organs, is one of the first and crucial steps of the metastasis cascade3. Thus these enzymes represent a prime target for the design of glycosylation inhibitors with the potential to specifically alter the structure of cell surface glycoproteins.