Superball! A dodecavalent iminosugar derivative with a fullerene core (see picture) shows a binding enhancement of up to three orders of magnitude over the corresponding monovalent ligand in glycosidase inhibition assays. This is the first evidence of a significant multivalent effect in glycosidase inhibition.

Superball! Ein dodekavalentes Iminozucker‐Derivat mit einem Fulleren‐Kern (siehe Bild) zeigt in Versuchen zur Glycosidase‐Inhibition eine um bis zu drei Größenordnungen bessere Bindung als der entsprechende monovalente Ligand. Dies ist der erste Beleg für einen signifikanten Multivalenzeffekt bei der Glycosidase‐Inhibition.

Pushing C–H amination to its limits fosters innovative synthetic solutions and offers a deeper understanding of the reaction mechanism and scope.

We describe herein a convenient strategy for the construction of C,C-glycoside building blocks via the intermediacy of tertiary pseudoanomeric radicals. Application of an iron-mediated hydrogen atom transfer/Michael−Giese coupling enables the anomeric quaternization of readily available exo-glycals with good to complete stereocontrol in the pyranose and furanose series. Carefully optimized conditions allow the use of challenging trisubstituted derivatives prone to undergo further elaboration to stable neoglycoconjugates. Preliminary results for direct C-disaccharide synthesis are also discussed.

The intermolecular C–O coupling reaction of 1,4-quinones with exo-glycals under iron hydride hydrogen atom transfer (HAT) conditions is described. This method provides a direct and regioselective access to a wide range of phenolic O-ketosides related to biologically relevant natural products in diastereomeric ratios up to >98:2 in the furanose and pyranose series. No trace of the corresponding C-glycosylated products that might have resulted from the radical alkylation of 1,4-quinones was observed. The results of mechanistic experiments suggest that the key C–O bond-forming event proceeds through an oxidative radical–polar crossover process involving a single-electron transfer between the HAT-generated glycosyl radical and the electron-acceptor quinone.

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The formation of carbon-carbon bonds with the control of multiple stereocenters in a single operation is not only a synthetic challenge but also a useful method for the construction of complex molecules. Tandem reactions are a very powerful example of a methodology used to achieve these aims.[1] Substituted chiral cyclohexanes are important building blocks in organic synthesis, and the control of the relative and absolute configurations is a key issue in the preparation of these versatile frameworks. The Diels-Alder cycloaddition is one widely employed method for the catalytic enantioselective synthesis of cyclohexane derivatives, most often catalyzed by either a chiral Lewis acid [2] or one of the recently developed chiral organocatalysts. [3] Many effective organocatalysts have been developed in recent years, [4] and chiral cyclohexanes and cyclohexenes have been synthesized by organocatalysts with high enantioselectivity.[5] Diarylprolinol silyl ether, which was originally developed by Jørgensens [5c,d,f, 6] and our groups [7] independently, has recently been utilized in several enantioselective reactions.[8] We have found that diphenylprolinol silyl ether is an effective organocatalyst for the direct enantioselective Michael reaction of aldehydes and nitroalkenes to afford the Michael adduct with high syn selectivity and excellent enantioselectivity.[7a] After our discovery, diphenylprolinol methyl ether was found to promote the enantioselective Michael reaction of aldehydes and methyl vinyl ketone, [8a] and Enders and co-workers expanded our reaction to a triple cascade reaction for the synthesis of chiral cyclohexenecarbaldehydes with control of four stereocenters in one operation.[5e] Just recently, Jørgensen and co-workers also reported a triple cascade reaction involving diarylprolinol silyl ether.[5f] As a further application of this organocatalyst in asymmetric reactions, we have developed a highly enantioselective tandem Michael [9] /Henry [10] reaction, which affords, in a single operation, substituted chiral nitrocyclohexanecarbaldehydes with excellent diastereo-and enantioselectivities and control of four stereogenic centers.We anticipated that pentane-1,5-dial and a nitroalkene would act as a four-carbon unit and a two-carbon unit, respectively. That is, as shown in Scheme 1, we hypothesized that enamine 2 would be generated from pentane-1,5-dial and catalyst 1 and that it would react with a nitroalkene in a Michael reaction to generate 3, in accordance with our previous findings.[7a] Zwitterion 3 would then react with the aldehyde moiety in an intramolecular Henry reaction to provide 4, which would be hydrolyzed to provide substituted nitrocyclohexanecarbaldehyde 5. The order of these last two reactions might be reversed (that is, hydrolysis of iminium ion 3 followed by the Henry reaction might provide 5).It would be convenient if commercially available aqueous 2,5-dihydroxy-3,4-dihydrofuran solution [11] could be used as a surrogate for pentane-1,5-dial. Pentane-1,5-dial would be generated...

Efficient deoxygenation methods are needed now more than ever in the chemist's toolbox to convert biomass‐derived molecules such as carbohydrates into useful chemicals. Late‐stage deoxygenation of drug candidates constitutes also an interesting option to fine tune their drug‐like properties. Metal‐based processes, as exemplified by the Barton–McCombie reaction, have long dominated the field. The development of metal‐free alcohol deoxygenation reactions represents however a challenge that has to be tackled to circumvent drawbacks associated with metal‐based reagents including cost and toxicity. Deoxygenation of alcohols may be assisted by the presence in α‐position of an electron‐withdrawing group. This review provides an overview of metal‐free methods that have been developed in the past decades for the direct, one‐step deoxygenation of α‐hydroxyl carbonyl compounds.