Oligosaccharides or glycans are essential in nature and central participants in virtually every biological process. The extensive structural diversity enables glycans to encode rich information in biological functions; however, it also creates major challenges in almost all aspects of the glycosciences. The synthetic formation of glycosidic bonds during glycan assembly, for example, is mechanistically still not fully understood. This is largely a result of highly-reactive, but short-lived oxocarbenium ion intermediates, which are difficult to study using established techniques. However, the structure of these intermediates dictates the stereochemistry of the resulting glycosidic bond, the control of which is absolutely crucial for a successful synthesis. The aim of GlycoCat is to unravel fundamental aspects of oligosaccharide reactions by probing cationic glycan intermediates. To do so, a unique combination of method development, chemical synthesis and theory will be used. In particular, different glycosyl cations bearing both participating (e.g. OAc or OBz) or non-participating (e.g. OBn) protecting groups will be screened with cold-ion IR spectroscopy to determine their conformation by comparing theoretical and experimental spectra. The gain in mechanistic understanding will provide the basis to tailor building blocks and reaction conditions. Eventually, this is expected to lead to a major advancement in glycosynthesis.