Using the Vapourtec R-Series flow chemistry system researchers from the Institut de Chemie des Substances Naturelles and the Institut des Sciences Moleculaires (CNRS) have shown the efficient and highly selective glycosylation of peracetylated β-D-N-acetyl gluco and galactosamines using catalytic iron (III) triflate under continuous flow conditions.
N-acetylated-D-glucosamine residues are important in biological structures and in small molecules for a range of bioactivities. The formation of the glycosidic link through glycosylation is often the biggest challenge in the synthesis of these compounds.
Common methods of b-selective glycosylation use donors with complex leaving groups in the anomeric position, however methods using glycosyl acetate donors offer a straight forward alternative to these. CNRS have shown mild conditions using iron (III) triflate as a cheap, non-toxic and environmentally friendly alternative to previously reported metal catalysts.
The methodology was developed under microwave conditions but it was soon found that scaling the reaction was limited due to the maximum reactor volume. Translating their conditions onto the Vapourtec R-Series allowed the group to further optimise the glycosylation reaction eliminating the need for TTBP.
The group were then able to demonstrate, with no further optimisation, the ability to scale the reaction beyond the scale limitations of the original microwave technique. A range of β-glycosides and β-linked disaccharides with various protecting groups were obtained in high yields using a step-saving method reducing the route to bioactive glycoconjugates.Find out more Published Papers
Have a look at the Organic Chemistry Frontiers paper