Regioselective Oxidation of Unprotected Carbohydrates and Their Further Functionalization

Functional group transformations in carbohydrates currently often rely on the use of protecting groups and the direct modification of unprotected carbohydrates remains a formidable challenge. [1] In our group an protocol has been developed that regioselectively oxidizes the C-3 hydroxyl group in a broad range of saccharides, including oligosaccharides, to a ketone by a palladium catalyst. [2] This ketone functionality is a versatile handle for further modification, although modification of keto-saccharides, without protecting groups is still under-investigated.

In this project, methyl 3-keto-D-glucose was taken as a model substrate and a plethora of reactions was studied for their compatibility with hydroxyl groups and polar solvents, such as water. The successful transformations resulted for example in synthesis of branched-chain sugars, which are rare motifs found in bacterial sugars. Furthermore, labels and reactive groups could be introduced into the keto-saccharide in one step, that are useful in the field of chemical biology.