Visible-light-promoted direct desulfurization of glycosyl thiols to access C-glycosides.

C-Glycosides are essential for the study of biological processes and the development of carbohydrate-based drugs. Despite the tremendous hurdles, glycochemists have often fantasized about the efficient, highly stereoselective synthesis of C-glycosides with the shortest steps under mild conditions. Herein, we report a desulfurative radical protocol to synthesize C-alkyl glycosides and coumarin C-glycosides under visible-light induced conditions without the need of an extra photocatalyst, in which stable and readily available glycosyl thiols that could be readily obtained from native sugars are activated in situ by pentafluoropyridine.

Stereoselective synthesis of α-glycosyl azides: allyl glycosyl sulfones as radical precursors.

Despite their critical importance in drug development and biochemistry, efficiently synthesizing α-glycosyl azides has continued to pose significant challenges. In this report, we introduce a universal and practical radical reaction for the stereoselective synthesis of α-glycosyl azides using bench-stable allyl glycosyl sulfones as the donor. This method is characterized by its mild reaction conditions, high stereoselectivity, and extensive scope of glycosyl units.

Controllable 1,3-Bis-Functionalization of 2-Nitroglycals with High Regioselectivity and Stereoselectivity Enabled by a H-Bond Catalyst.

The selective modification of carbohydrates is significant for producing their unnatural analogues for drug discovery. C1-functionalization (glycosylation) and C1,C2-difunctionalization of carbohydrates have been well developed. In contrast, C3-functionalization or C1,C3-difunctionalization of carbohydrates remains rare.

Nickel and Chiral Phosphoric Acid Cocatalysis Enables Synthesis of -Acyl Glycosides.

We disclosed a Ni/CPA cocatalyzed protocol to access diverse -acyl glycosides under mild conditions with broad functional group compatibility through the coupling of readily available glycosyl bromides and carboxylic esters. The potential application of the methodology was demonstrated by the -acyl glycosylation of bioactive molecules and the transformation of products to a variety of value-added molecules. Mechanistic studies revealed that CPA might serve as a bifunctional H-bond catalyst to activate carboxylic esters and nickel catalyst.

Recent Advances in Chemical Synthesis of Amino Sugars.

Amino sugars are a kind of carbohydrates with one or more hydroxyl groups replaced by an amino group. They play crucial roles in a broad range of biological activities. Over the past few decades, there have been continuing efforts on the stereoselective glycosylation of amino sugars.

Alkyl/Glycosyl Sulfoxides as Radical Precursors and Their Use in the Synthesis of Pyridine Derivatives.

We report here the use of simple and readily available alkyl sulfoxides as precursors to radicals and their application in the preparation of pyridine derivatives. We show that alkyl sulfoxides, N-methoxy pyridinium salts and fluoride anions form electron donor-acceptor (EDA) complexes in solution, which, upon visible light irradiation, undergo a radical chain process to afford various pyridine derivatives smoothly. This reaction displays broad scope with respect to both sulfoxides and N-methoxy pyridiniums.

Selective synthesis of enol ethers nickel-catalyzed cross coupling of α-oxy-vinylsulfones with alkylzinc reagents.

We describe here a Ni-catalyzed Negishi coupling reaction to prepare 1,2-dialkyl enol ethers in a stereoconvergent fashion. This method employs readily available and bench-stable α-oxy-vinylsulfones as electrophiles. The C-sulfone bond in the α-oxy-vinylsulfone motif is cleaved chemoselectively in these reactions.