Allyl Cyanate/Isocyanate Rearrangement in Glycals: Stereoselective Synthesis of 1-Amino and Diamino Sugar Derivatives.

The [3,3]-sigmatropic allyl cyanate/isocyanate rearrangement of glycals in the presence of O-, N-, and C-nucleophiles afforded ß-N-glucosyl and galactosyl carbamates, ureas, and amides in good yields. The unsaturated products were elaborated to N-glycosides by dihydroxylation, to 1,3-diaminosugars by tethered aminohydroxylation, or to 1,2-diaminosugars by iteration of the sigmatropic rearrangement. This metal-free methodology represents an excellent and general method for the stereoselective synthesis of N-glycosides and diamino sugars with complete transmission of stereochemical information.

Mechanistic Insight into the Binding of Multivalent Pyrrolidines to α-Mannosidases.

Novel pyrrolidine-based multivalent iminosugars, synthesized by a CuAAC approach, have shown remarkable multivalent effects towards jack bean α-mannosidase and a Golgi α-mannosidase from Drosophila melanogaster, as well as a good selectivity with respect to a lysosomal α-mannosidase, which is important for anticancer applications. STD NMR and molecular modeling studies supported a multivalent mechanism with specific interactions of the bioactive iminosugars with Jack bean α-mannosidase. TEM studies suggested a binding mode that involves the formation of aggregates, which result from the intermolecular cross-linked network of interactions between the multivalent inhibitors and two or more dimers of JBMan heterodimeric subunits.

Glycans in Infectious Diseases. A Molecular Recognition Perspective.

BACKGROUND: From the simplest bacteria to the highest complex mammals, including humans, every single cell is covered by a dense coat of glycans. Glycans are involved in almost every biological process that takes place in our body, playing a central role in the communication between cells and their environment. Glycans are also involved in infectious diseases, which arise from the specific interaction between glycans of the pathogen cell coat and specific receptors on the host cell or vice versa. OBJECTIVE: The understanding of the mechanisms governing these specific carbohydrateprotein interactions, at atomic and molecular levels, is crucial to develop new drugs able to block the infection and to avoid the disease. METHODS: Recent advances in biophysical techniques allow for a complete picture of the hostpathogen infection event, unveiling the key aspects of the molecular interaction and, thus, providing an opportunity to interfere with it. CONCLUSION: In this general review, we discuss some recent contributions, providing a summary of what we consider the most innovative and inspiring research lines to the field.

Osmium-catalyzed tethered aminohydroxylation of glycals: a stereodirected access to 2- and 3-aminosugars.

The osmium-catalyzed aminohydroxylation of glycals has been achieved with complete regio- and stereocontrol by taking advantage of the Donohoe tethering approach. Glucals and galactals showed complementary reactivity in dependence of the stage at which the reaction was performed, i.e., directly or after double-bond shift consequent to a Ferrier rearrangement (that is, on the 1,2 or 2,3-unsaturated sugar), allowing access to both classes of 2-amino (mannosamine) and 3-amino (talosamine) sugar derivatives, respectively.

Exploring architectures displaying multimeric presentations of a trihydroxypiperidine iminosugar.

The synthesis of new multivalent architectures based on a trihydroxypiperidine α-fucosidase inhibitor is reported herein. Tetravalent and nonavalent dendrimers were obtained by means of the click chemistry approach involving the copper azide-alkyne-catalyzed cycloaddition (CuAAC) between suitable scaffolds bearing terminal alkyne moieties and an azido-functionalized piperidine as the bioactive moiety. A preliminary biological investigation is also reported towards commercially available and human glycosidases.