In the 1890s, Emil Fischer introduced the glycosylation reaction that became crucial in the chemical assembly of carbohydrates. The reaction is believed to proceed under most reaction conditions via a key ionic species, the glycosyl oxocarbenium ion. However, the transient nature of this short-lived reaction intermediate impeded its isolation and detailed structural characterization. Here, we report an in-depth structural analysis of glycosyl cations using a combination of cold-ion infrared spectroscopy and first-principles theory. Participating C2 protective groups form indeed a covalent bond with the anomeric carbon that leads to C1-bridged acetoxonium-type structures. The resulting bicyclic structure strongly distorts the ring, which leads to a unique conformation for each individual monosaccharide. This gain in mechanistic understanding fundamentally impacts glycosynthesis and will allow to tailor building blocks and reaction conditions in the future.

Go to article: https://www.nature.com/articles/s41467-018-06764-3

FU Press Release: https://www.fu-berlin.de/presse/informationen/fup/2018/fup_18_262-reaktiver-zucker-studie/index.html