Tunable Light-Activated Platform for Controlled Hydrogen Sulfide Release with Tracking.

Hydrogen sulfide (H2S) is increasingly recognized for its critical roles in various physiological and pathological processes. The development of synthetic donors with controllable release profiles is essential for elucidating H2S's complex involvement in cellular signaling, which remains a challenge. Herein, we report a diverse collection of photocaged N-methylation thiocarbamates and thiocarbonates, designed to explore how electronic properties and the leaving efficiency of payloads affect H2S release behaviors.

Gold(I)-Catalyzed 2-Deoxy-β-glycosylation via 1,2-Alkyl/Arylthio Migration: Synthesis of Velutinoside A Pentasaccharide.

2-Deoxy-β-glycosides are essential components of natural products and pharmaceuticals; however, the corresponding 2-deoxy-β-glycosidic bonds are challenging to chemically construct. Herein, we describe an efficient catalytic protocol for synthesizing 2-deoxy-β-glycosides via either IPrAuNTf-catalyzed activation of a unique 1,2--positioned C2--propargyl xanthate (OSPX) leaving group or (PhO)PAuNTf-catalyzed activation of a 1,2--C2--alkynylbenzoate (OABz) substituent of the corresponding thioglycosides. These activation processes trigger 1,2-alkyl/arylthio-migration glycosylation, enabling the synthesis of structurally diverse 2-deoxy-β-glycosides under mild reaction conditions.

Zinc(ii)-mediated stereoselective construction of 1,2- 2-azido-2-deoxy glycosidic linkage: assembly of K48 capsular pentasaccharide derivative.

The capsular polysaccharide (CPS) is a major virulence factor of the pathogenic and a promising target for vaccine development. However, the synthesis of the 1,2--2-amino-2-deoxyglycoside core of CPS remains challenging to date. Here we develop a highly α-selective ZnI-mediated 1,2- 2-azido-2-deoxy chemical glycosylation strategy using 2-azido-2-deoxy glucosyl donors equipped with various 4,6--tethered groups.

A Strain-Promoted Divergent Chemical Steroidation Unveils Potent Anti-Inflammatory Pseudo-Steroidal Glycosides.

The development of novel agents with immunoregulatory effects is a keen way to combat the growing threat of inflammatory storms to global health. To synthesize pseudo-steroidal glycosides tethered by ether bonds with promising immunomodulatory potential, we develop herein a highly effective deoxygenative functionalization of a novel steroidal donor (steroidation) facilitated by strain-release, leveraging cost-effective and readily available Sc(OTf) catalysis. This transformation produces a transient steroid-3-yl carbocation which readily reacts with -, -, -, -, and -nucleophiles to generate structurally diverse steroid derivatives.

GlcNAc-1,6-anhydro-MurNAc Moiety Affords Unusual Glycosyl Acceptor that Terminates Peptidoglycan Elongation.

Peptidoglycan (PG), an essential exoskeletal polymer in bacteria, is a well-known antibiotic target. PG polymerization requires the action of bacterial transglycosylases (TGases), which couple the incoming glycosyl acceptor to the donor. Interfering with the TGase activity can interrupt the PG assembly.

Cobalt's Dual Role in Promoting C3-Glycosylation of Indoles: Unraveling Mechanistic Insights.

In this study, we present a cobalt-catalyzed C3-glycosylation of indoles using unfunctionalized glycals, yielding 3-indolyl--deoxyglycosides. These compounds hold promise as sodium-dependent glucose cotransporter 2 (SGLT2) inhibitors for treating type 2 diabetes. Control experiments unveiled that cobalt assumes a dual role, facilitating catalytic -glycosylation while unexpectedly driving the anomerization of α-anomers through endocyclic cleavage of the C1-O5 bond, resulting in the formation of β--deoxyglycosides.

ZnI-Mediated β-Galactosylation of C2-Ether-Type Donor.

Conventional glycosylation with galactosyl donors having C-2 benzyl (Bn) ether-type functionality often leads to anomeric mixtures, due to the anomeric and steric effects that stabilize the 1,2--α- and 1,2--β-glycosides, respectively. Herein we report a versatile ZnI-directed β-galactosylation approach employing a 4,6--tethered and 2--Bn galactosyl donor for the stereoselective and efficient synthesis of β--galactosides. With a broad substrate scope, the reaction tolerates a wide range of functional groups and complex molecular architectures, providing stereocontrolled β-galactosides in moderate to excellent yields.

Zinc(II) Iodide-Directed β-Mannosylation: Reaction Selectivity, Mode, and Application.

A direct, efficient, and versatile glycosylation methodology promises the systematic synthesis of oligosaccharides and glycoconjugates in a streamlined fashion like the synthesis of medium to long-chain nucleotides and peptides. The development of a generally applicable approach for the construction of 1,2--glycosidic bond with controlled stereoselectivity remains a major challenge, especially for the synthesis of β-mannosides. Here, we report a direct mannosylation strategy mediated by ZnI, a mild Lewis acid, for the highly stereoselective construction of 1,2--β linkages employing easily accessible 4,6--tethered mannosyl trichloroacetimidate donors.

ZnI-Directed Stereocontrolled α-Glucosylation.

Here we report a glucosylation strategy mediated by ZnI, a cheap and mild Lewis acid, for the highly stereoselective construction of 1,2---glycosidic linkages using easily accessible and common 4,6--tethered glucosyl donors. The versatility and effectiveness of the α-glucosylation strategy were demonstrated successfully with various acceptors, including complex alcohols. This approach demonstrates the feasibility of the modular synthesis of various α-glucans with both linear and branched backbone structures.

Iridium-promoted deoxyglycoside synthesis: stereoselectivity and mechanistic insight.

Herein, we devised a method for stereoselective -glycosylation using an Ir(i)-catalyst which enables both hydroalkoxylation and nucleophilic substitution of glycals with varying substituents at the C3 position. In this transformation, 2-deoxy-α--glycosides were acquired when glycals equipped with a notoriously poor leaving group at C3 were used; in contrast 2,3-unsaturated-α--glycosides were produced from glycals that bear a good leaving group at C3. Mechanistic studies indicate that both reactions proceed the directing mechanism, through which the acceptor coordinates to the Ir(i) metal in the α-face-coordinated Ir(i)-glycal π-complex and then attacks the glycal that contains the -glycosidic bond in a -addition manner.