Carbene-Mediated Quaternarization of the Anomeric Position of Carbohydrates: Synthesis of Allylic Ketopyranosides, Access to the Missing α-Gluco and β-Manno Stereoisomers, and Preparation of Quaternary 2-Deoxy 2-Acetamido Sugars

Ferrier/Aza-Wacker/Epoxidation/Glycosylation (FAWEG) Sequence to Access 1,2-Trans 3-Amino-3-deoxyglycosides

3-Amino-3-deoxyglycosides constitute an essential class of nitrogen-containing sugars. Among them, many important 3-amino-3-deoxyglycosides possess a 1,2-trans relationship. In view of their numerous biological applications, the synthesis of 3-amino-3-deoxyglycosyl donors giving rise to a 1,2-trans glycosidic linkage is thus an important challenge. Even though glycals are highly polyvalent donors, the synthesis and reactivity of 3-amino-3-deoxyglycals have been little studied. In this work, we describe a new sequence, involving a Ferrier rearrangement and subsequent aza-Wacker cyclization that allows the rapid synthesis of orthogonally protected 3-amino-3-deoxyglycals. Finally a 3-amino-3-deoxygalactal derivative was submitted for the first time to an epoxidation/glycosylation with high yield and great diastereoselectivity, highlighting FAWEG (Ferrier/Aza-Wacker/Epoxidation/Glycosylation) as a new approach to access 1,2-trans 3-amino-3-deoxyglycosides.

Tunable Approach to C-Linked Analogs of Glycosamines

The synthesis of (1R)-2-amino-2-deoxy-β-l-gulopyranosyl benzene and the α and β forms of 2-amino-2-deoxy-l-idopyranosyl benzene derivatives was accomplished through stereospecific addition of tributylstannyllithium to readily available (S_R)- or (S_S)-N-tert-butanesulfinyl-arabinofuranosylamine building blocks, followed by stereoretentive Pd-catalyzed Migita-Kosugi-Stille cross-coupling, stereoselective reduction, and an activation-cyclization strategy. Application of this methodology paves the way to new three-dimensional chemical space and preparation of unknown (non-natural) and complex 2-amino-2-deoxy sugars of biological interest.

Preparation of propargyl 1,2-orthoesters of carbohydrates: From side reactions in dichloromethane to optimized reaction conditions in acetonitrile

In this note, supercritical fluid chromatography coupled to high-resolution mass spectrometry (SFC-HRMS) has been used to identify a chloro glycoside formed during the preparation of propargyl 1,2-orthoesters in dichloromethane. Additional studies revealed that 20-40% of this side-product was obtained depending on the source of anhydrous solvent, and that tetrabutylammonium iodide amplifies this side-reaction. Finally, a reliable procedure was developed in acetonitrile to prepare these glycosyl donors from perbenzoylated bromo glycosides in manno, gluco and galacto series in 63-74% yield.

Hydrozirconation/bromination, followed by a Michaelis-Arbuzov reaction, as a convenient approach towards polyfunctional glycosylphosphonates

In this note, an hydrozirconation/bromination/Michaelis-Arbuzov sequence was developped to introduce a trimethylene phosphonate unit on ketopyranosides. Performed on polyfunctional substrates bearing orthogonal protecting groups, this new approach provided a straightforward entry towards a large diversity of glycophosphomimetics having a quaternary anomeric position.