The stereoselective synthesis of glycosides remains one of the biggest challenges in carbohydrate chemistry.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;The chemical synthesis of complex carbohydrates generally involves the coupling of a fully protected glycosyl donor bearing a leaving group at its anomeric centre, with a suitably protected glycosyl acceptor (R-OH). In many instances, these reactions lead to a mixture of two stereoisomers.<br/>In recent years, our group has endeavoured to develop catalytic and stereoselective methods to address this important synthetic challenge.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;Recent years have seen a steady increase in the application of transition metal catalysis applied to oligosaccharide synthesis,&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;since the reaction conditions are mild and the careful choice of catalyst can offer significant improvements over traditional methods in terms of atom economy, high yields and control of anomeric selectivity.<br/>Herein, we will report that tuning the reactivity of Cu by the choice of oxidation state and counterion leads to the activation of both “armed” and “disarmed” type glycals toward direct glycosylation leading to the α-stereoselective synthesis of deoxyglycosides in good to excellent yields.&lt;span style="font-size:10.8333px"&gt; &lt;/span&gt;Mechanistic studies show that Cu (I) is essential for effective catalysis and stereocontrol and that the reaction proceeds through dual activation of both the enol ether as well as the OH nucleophile.

Catalytic stereoselective synthesis of glycosides. Old catalysts, new tricks

ACS Fall 2020 Virtual Meeting

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