Stereoselective Synthesis of C-Vinyl Glycosides via Palladium-Catalyzed C-H Glycosylation of Alkenes

Stereoselective P(III)-Glycosylation for the Preparation of Phosphinated Sugars

Most of the reported work focus on the development of O-, N-, C- and S-glycosylation methods. However, no study explores P(III)-glycosylation reaction. Herein we describe a convenient protocol to realize P(III)-glycosylation process. A simple β-phosphino ester is adopted as P(III)-transfer reagent for this new type of glycosylation via a nucleophilic substitution and release strategy. Diverse phosphine units are introduced to the anomeric center of various sugars efficiently and with excellent stereoselectivity. The value of this method is showcased by the prepared P(III)-sugars as novel linkers in bioactive molecule conjugation, new chiral ligands in metal-catalyzed asymmetric allylic substitutions and organocatalysts. Preliminary mechanistic studies corroborated the designed P(III)-transfer process.

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. The benefits of this procedure include high stereoselectivity, broad substrate scope, and easy handling. Mechanistic studies indicate that the in situ produced tetrafluoropyridyl S-glycosides form key electron donor-acceptor (EDA) complexes with Hantzsch ester (for C-alkyl glycosides) or Et3N (for coumarin C-glycosides), which, upon irradiation with visible light, trigger a cascade of glycosyl radical processes to access C-glycosides smoothly.

Concise synthesis of 3-C-glycosyl isocoumarins and 2-glycosyl-4H-chromen-4-ones

A new Ru-catalyzed C-H activation/cyclization reaction for the synthesis of 3-C-glycosyl isocoumarins and 2-glycosyl-4H-chromen-4-ones with carbonyl sulfoxonium ylide glycogen are reported. In this catalytic system, benzoic acid and its derivatives react with carbonyl sulfoxonium ylide glycogen to yield isocoumarin C-glycosides, while 2-hydroxybenzaldehyde substrates react to produce chromone C-glycosides. These reactions were characterized by mild reaction conditions, broad substrate scope, high functional-group compatibility, and high stereoselectivity to yield several high-value isocoumarins and chromone skeleton-containing C-glycosides. The methods were successfully implemented in the context of large-scale reactions and the late-stage modification of complex natural products.

Stereoselective and site-divergent synthesis of C-glycosides

Carbohydrates play important roles in medicinal chemistry and biochemistry. However, their synthesis relies on specially designed glycosyl donors, which are often unstable and require multi-step synthesis. Furthermore, the catalytic and stereoselective installation of arylated quaternary stereocentres on sugar rings remains a formidable challenge. Here we report a facile and versatile method for the synthesis of diverse C-R (where R is an aryl, heteroaryl, alkenyl, alkynyl or alkyl) glycosides from readily available and bench-stable 1-deoxyglycosides. The reaction proceeds under mild conditions and exhibits high stereoselectivity across a broad range of glycosyl units. This protocol can be used to synthesize challenging 2-deoxyglycosides, unprotected glycosides, non-classical glycosides and deuterated glycosides. We further developed the catalyst-controlled site-divergent functionalization of carbohydrates for the synthesis of various unexplored carbohydrates containing arylated quaternary stereocentres that are inaccessible by existing methods. The synthetic utility of this strategy is further demonstrated in the synthesis of pharmaceutically relevant molecules and carbohydrates.

Linkage-Editing of Melibiosamine: Synthesis and Biological Evaluation of CH2- and CHF-Linked Analogs

Melibiosamine (Gal-α(1,6)-GlcNH2), consisting of galactose and glucosamine linked by an α(1,6)-glycosidic bond, is an artificial disaccharide derivative that selectively inhibits the proliferation of K562 tumor cells relative to HUC-F2 normal cells. In this study, we employed a linkage-editing strategy to synthesize CH2- and CHF-linked melibiosamine analogs through chemo- and stereoselective hydrogenation of fluorovinyl-C-glycoside. (R)-CHF-Melibiosamine exhibited more potent antiproliferative activity than O-linked melibiosamine, while (S)-CHF-melibiosamine was less potent.

A Radical Activation Strategy for Versatile and Stereoselective N-Glycosylation

Previous N-glycosylation approaches have predominately involved acidic conditions, facing challenges of low stereoselectivity and limited scope. Herein, we introduce a radical activation strategy that enables versatile and stereoselective N-glycosylation using readily accessible glycosyl sulfinate donors under basic conditions and exhibits exceptional tolerance towards various N-aglycones containing alkyl, aryl, heteroaryl and nucleobase functionalities. Preliminary mechanistic studies indicate a pivotal role of iodide, which orchestrates the formation of a glycosyl radical from the glycosyl sulfinate and subsequent generation of the key intermediate, a configurationally well-defined glycosyl iodide, which is subsequently attacked by an N-aglycone in a stereospecific SN2 manner to give the desired N-glycosides. An alternative route involving the coupling of a glycosyl radical and a nitrogen-centered radical is also proposed, affording the exclusive 1,2-trans product. This novel approach promises to broaden the synthetic landscape of N-glycosides, offering a powerful tool for the construction of complex glycosidic structures under mild conditions.

Directed copper-catalyzed C-H functionalization of unactivated olefins with azodicarbonamide compounds

The copper-catalyzed strategy employing the 8-aminoquinoline directing group has proven to be a highly advantageous approach for functionalizing C-H bonds. In this study, we present the successful application of this strategy to accomplish Heck-type coupling reactions and construct β-lactam skeletons, simultaneously introducing a unique cyano functional group. The resulting Heck-type coupling products demonstrate good stereo- and region-selectivity. Initial mechanistic investigations indicate that the reaction proceeds via a radical coupling mechanism, exhibiting a wide substrate scope and delivering good yields.

Synthesis of C-Alkyl Glycosides from Alkyl Bromides and Glycosyl Carboxylic Acids via Ni/Photoredox Dual Catalysis

C-Alkyl glycosides, an important class of C-glycosides, are widely found in various drugs and natural products. The synthesis of C-alkyl glycosides has attracted considerable attention. Herein, we developed a Ni/photoredox catalyzed decarboxylative C(sp3)-C(sp3) coupling reaction of stable glycosylcarboxylic acids with simple aliphatic bromides to generate C-alkyl glycosides. The method successfully linked several functional molecular fragments (natural products or drugs) to a sugar moiety, showing the extensive application prospects of this transformation. Controlled experiments and DFT calculations demonstrated that the reaction pathway contains a free radical process, and a possible mechanism is proposed.

Electrochemical Glycosylation via Halogen-Atom-Transfer for C-Glycoside Assembly

Glycosyl donor activation emerged as an enabling technology for anomeric functionalization, but aimed primarily at O-glycosylation. In contrast, we herein disclose mechanistically distinct electrochemical glycosyl bromide donor activations via halogen-atom transfer and anomeric C-glycosylation. The anomeric radical addition to alkenes led to C-alkyl glycoside synthesis under precious metal-free reaction conditions from readily available glycosyl bromides. The robustness of our e-XAT strategy was further mirrored by C-aryl and C-acyl glycosides assembly through nickela-electrocatalysis. Our approach provides an orthogonal strategy for glycosyl donor activation with expedient scope, hence representing a general method for direct C-glycosides assembly.

Preparing glycosyl benzothiazoles from 2-isocyanoaryl thioethers and glycosyl radicals under thermal conditions

Herein, we report a method for preparing glycosyl benzothiazoles via radical cascade cyclization, in which glycosyl radicals are generated from readily available and bench-stable allyl glycosyl sulfones. This cascade reaction proceeds under simple conditions and tolerates a broad substrate scope in high yield with excellent stereoselectivity. Mechanistic studies support that the reactions proceed via the intermediacy of imidoyl radicals, which attack the appended sulfide unit by a SH2 process to forge the thiazole ring.

Stereoselective assembly of C-oligosaccharides via modular difunctionalization of glycals

C-oligosaccharides are found in natural products and drug molecules. Despite the considerable progress made during the last decades, modular and stereoselective synthesis of C-oligosaccharides continues to be challenging and underdeveloped compared to the synthesis technology of O-oligosaccharides. Herein, we design a distinct strategy for the stereoselective and efficient synthesis of C-oligosaccharides via palladium-catalyzed nondirected C1-H glycosylation/C2-alkenylation, cyanation, and alkynylation of 2-iodoglycals with glycosyl chloride donors while realizing the difunctionalization of 2-iodoglycals. The catalysis approach tolerates various functional groups, including derivatives of marketed drugs and natural products. Notably, the obtained C-oligosaccharides can be further transformed into various C-glycosides while fully conserving the stereochemistry. The results of density functional theory (DFT) calculations support oxidative addition mechanism of alkenyl-norbornyl-palladacycle (ANP) intermediate with α-mannofuranose chloride and the high stereoselectivity of glycosylation is due to steric hindrance.

Direct Construction of C-Alkyl Glycosides from Non-Activated Olefins via Nickel-Catalyzed C(sp3)─C(sp3) Coupling Reaction

Among C-glycosides, C-alkyl glycosides are significant building blocks for natural products and glycopeptides. However, research on efficient construction methods for C-alkyl glycosides remains relatively limited. Compared with Michael acceptors, non-activated olefins are more challenging substrates and have rarely been employed in the construction of C-glycosides. Here, a highly efficient and convenient approach for the synthesis of C-alkyl glycosides through a nickel-catalyzed C(sp3)-C(sp3) coupling reaction is presented. A distinctive feature of this method is its utilization of non-activated olefins as the anomeric radical acceptors for hydroalkylation, allowing for the direct formation of C-glycoside bonds in a single step. Furthermore, this method demonstrates excellent compatibility with a broad scope of highly reactive functional groups. Mechanistic investigations suggest that the reaction proceeds via a free radical pathway, leading predominantly to the formation of products with α-configuration. Overall, this innovative methodology offers a versatile and practical approach for the synthesis of C-alkyl glycosides, offering new avenues for the production of intricate glycosides with potential applications in drug discovery and chemical biology.

Exploiting π and Chalcogen Interactions for the β-Selective Glycosylation of Indoles through Glycal Conformational Distortion

Harnessing unconventional noncovalent interactions (NCIs) is emerging as a formidable synthetic approach in difficult-to-access glycosidic chemical space. C-Glycosylation, in particular, has gained a flurry of recent attention. However, most reported methods are restricted to the relatively facile access to α-C-glycosides. Herein, we disclose a β-stereoselective glycosylation of indoles by employing a phosphonoselenide catalyst. The robustness of this protocol is exemplified by its amenability for reaction at both the indolyl C- and N- reactivity sites. In contrast to previous reports, in which the chalcogens were solely involved in Lewis acidic activation, our mechanistic investigation unraveled that the often neglected flanking aromatic substituents of phosphonoselenides can substantially contribute to catalysis by engaging in π-interactions. Computations and NMR spectroscopy indicated that the chalcogenic and aromatic components of the catalyst can be collectively exploited to foster conformational distortion of the glycal away from the usual half-chair to the boat conformation, which liberates the convex β-face for nucleophilic attack.

Linkage-Editing Pseudo-Glycans: A Reductive α-Fluorovinyl-C-Glycosylation Strategy to Create Glycan Analogs with Altered Biological Activities

The acetal (O-glycoside) bonds of glycans and glycoconjugates are chemically and biologically vulnerable, and therefore C-glycosides are of interest as more stable analogs. We hypothesized that, if the O-glycoside linkage plays a vital role in glycan function, the biological activities of C-glycoside analogs would vary depending on their substituents. Based on this idea, we adopted a "linkage-editing strategy" for the creation of glycan analogs (pseudo-glycans). We designed three types of pseudo-glycans with CH2 and CHF linkages, which resemble the O-glycoside linkage in terms of bond lengths, angles, and bulkiness, and synthesized them efficiently by means of fluorovinyl C-glycosylation and selective hydrogenation reactions. Application of this strategy to isomaltose (IM), an inducer of amylase expression, and α-GalCer, which activates iNKT cells, resulted in the discovery of CH2-IM, which shows increased amylase production ability, and CHF-α-GalCer, which shows activity opposite that of native α-GalCer, serving as an antagonist of iNKT cells.

Mild method for the synthesis of α-glycosyl chlorides: A convenient protocol for quick one-pot glycosylation

A simple and efficient protocol for the preparation of α-glycosyl chlorides within 15-30 min is described which employs a stable, cheap, and commercially available Trichloroisocyanuric acid (TCCA) as non-toxic chlorinating agent along with PPh3. This process involved a wide range of substrate scope and is well-suited with labile hydroxyl protecting groups such as benzyl, acetyl, benzoyl, isopropylidene, benzylidene, and TBDPS (tert-butyldiphenylsilyl) groups. This process is operationally simple, mild conditions and obtained good yields with excellent α selectivity. Moreover, a multi-catalyst one-pot glycosylation can be carried out to transform the glycosyl hemiacetals directly to a various O-glycosides in high overall yields without the need for separation or purification of the α-glycosyl chloride donors.

Non-classical C-saccharide linkage of dehydroalanine: synthesis of C-glycoamino acids and C-glycopeptides

Herein, a non-classical C-saccharide linkage is reported via a C5 radical of pentose or C6 radical of hexose addition to Michael acceptors. C(sp³)-S cleaved glycosyl thianthrenium salts are developed as the glycosyl radical agents. The reaction provides an efficient toolkit to synthesize β-glycosyl substituted unnatural amino acids as well as for the late-stage C-saccharide modification of peptides.

Chemical synthesis of oligosaccharides and their application in new drug research

Oligosaccharides are the ubiquitous molecules of life. In order to translate human bioglycosylation into clinical applications, homogeneous samples of oligosaccharides and glycoconjugates can be obtained by chemical, enzymatic or other biological methods for systematic studies. However, the structural complexity and diversity of glycans and their conjugates present a major challenge for the synthesis of such molecules. This review summarizes the chemical synthesis methods of oligosaccharides, the application of oligosaccharides in the field of medicinal chemistry according to their related biological activities, and shows the great prospect of oligosaccharides in the field of pharmaceutical chemistry.

Generation and Use of Glycosyl Radicals under Acidic Conditions: Glycosyl Sulfinates as Precursors

We herein report a method that enables the generation of glycosyl radicals under highly acidic conditions. Key to the success is the design and use of glycosyl sulfinates as radical precursors, which are bench-stable solids and can be readily prepared from commercial starting materials. This development allows the installation of glycosyl units onto pyridine rings directly by the Minisci reaction. We further demonstrate the utility of this method in the late-stage modification of complex drug molecules, including the anticancer agent camptothecin. Experimental studies provide insight into the reaction mechanism.

Glycosyl Radical-Based Synthesis of C-Glycoamino Acids and C-Glycopeptides

Radical-based reactions usually exhibit excellent functional-group compatibilities due to their mild initiation conditions. Glycosyl radical involved C-glycosylation modifications are important strategies to achieve highly regio- and chemoselective constructions of C-glycosidic bonds or C-glycoside linkages of peptides and proteins. In this Concept, we cover recent developments in glycosyl radical-based synthesis of unnatural amino acids and late-stage modification of peptides and proteins, and provide a preliminary outlook on the possible development of this direction in the future.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

Palladium-Catalyzed Direct C-H Glycosylation of Free (N-H) Indole and Tryptophan by Norbornene-Mediated Regioselective C-H Activation

We describe the palladium-catalyzed direct C-H glycosylation of free N-H indole or tryptophan for the stereoselective synthesis of 2-glycosylindoles and tryptophan-C-glycosides. This reaction relies on the ortho-directing transient mediator norbornene, which underwent regioselective C-H functionalization at the indole or tryptophan ring, providing high chemoselectivity. This method offers a more straightforward, step-economical, and cost-effective route to construct C-glycosides. The gram-scale amenable building blocks can be further functionalized at C3 and N-H, displaying the robustness of present method.

Visible-Light-Induced Copper-Catalyzed Asymmetric C(sp3)-C(sp3)-H Glycosylation: Access to C-Glycopeptides

Herein, a practical and highly efficient method for visible-light-induced copper-catalyzed N-aminoquinoline-directed asymmetric C(sp³)-C(sp³)-H glycosylation was reported. At the same time, C(sp³)-C(sp³)-H glycosylation of nondeoxysugars with amino acids to construct C-glycopeptides was achieved. This approach promoted the synthesis of various C-glycopeptides and provided a new model for the synthesis of C-glycoamino acids.

Ruthenium-Catalyzed Pyridine-Directed Aryl C-H Glycosylation with Glycosyl Chlorides

Metal-catalyzed C-H glycosylation reactions with glycosyl chloride donors have emerged as a useful strategy for the synthesis of C-glycosides. Previously, palladium and nickel complexes were reported to catalyze C-H glycosylation reactions using amide-linked bidentate auxiliaries. Herein, a ruthenium-catalyzed ortho C-H glycosylation reaction of arenes with various glycosyl chloride donors using a monodentate pyridine directing group is developed. Preliminary mechanistic studies indicated that two-electron oxidative addition and reductive elimination of ruthenocycle intermediate led to the glycosylation products.

Preparation of glycosyl carboxylic acids via stereoselective synthesis and oxidative cleavage of C-vinyl glycosides

We have developed an improved cyanide-free strategy for the synthesis of glycosyl carboxylic acids, employing stereoselective C-vinyl glycosylation and oxidative cleavage of C-vinyl glycosides as key steps. Compared to our previous work, the amount of NaIO₄ required for the oxidative cleavage step is reduced significantly from 18 equivalents to 4.5 equivalents. This modification not only is advantageous in terms of operation and costs but also avoids the over-oxidation problem, thus greatly expanding the substrate scope, which is evidenced by the fact that 10 out of 21 glycosyl carboxylic acids synthesized are undocumented. With differently O5-protected furanosyl acids in hand, we demonstrate that an electron-rich protecting group is beneficial for the decarboxylative arylation of furanosyl carboxylic acids. This represents a rare example of protecting groups affecting the reaction efficiency in radical C-glycosylation. As C-vinyl glycosides can be prepared stereoselectively and the oxidative step is stereoretentive, the approach provides an effective means to access 1,2-trans or 1,2-cis glycosyl acids, which would be a valuable alternative to the cyanide-based synthesis of glycosyl carboxylic acids.

Directed Copper-Catalyzed Tandem Radical Cyclization Reaction of Alkyl Bromides and Unactivated Olefins

The free radical cyclization reaction is a promising strategy for ring framework formation. Herein, we report a copper-catalyzed tandem radical cyclization strategy for preparing substituted lactam derivatives. This reaction proceeds through a radical coupling approach, which not only allows a wide range of alkenes but also is quite compatible with the primary, secondary, and tertiary radicals. In addition, density functional theory calculations were performed to gain insights into the reaction mechanism.

One-Pot Stereoselective Synthesis of 2,3-Diglycosylindoles and Tryptophan-C-glycosides via Palladium-Catalyzed C-H Glycosylation of Indole and Tryptophan

We described a novel palladium-catalyzed C-H glycosylation of indole or tryptophan for a one-pot stereoselective synthesis of 2,3-diglycosylindoles and tryptophan-C-glycosides. In this strategy, the use of air and base-free and ligand-free conditions provided a highly efficient route to construct C-glycosides. The method can be applied to a wide range of cost-effective and convenient glycosyl chloride donors. Mechanistic studies indicated that the indole 2,3-diglycosylation sequence was C3 and then C2.

Synthesis of C-Oligosaccharides through Versatile C(sp3 )-H Glycosylation of Glycosides

C-oligosaccharides are pharmacologically relevant because they are more hydrolysis-resistant than O-oligosaccharides. Despite indisputable advances, C-oligosaccharides continue to be underdeveloped, likely due to a lack of efficient and selective strategies for the assembly of the interglycosidic C-C linkages. In contrast, we, herein, report a versatile and robust strategy for the synthesis of structurally complex C-oligosaccharides via catalyzed C(sp3 )-H activations. Thus, a wealth of complex interglycosidic (2→1)- and (1→1)-C-oligosaccharides becomes readily available by palladium-catalyzed C(sp3 )-H glycoside glycosylation. The isolation of key palladacycle intermediates and experiments with isotopically-labeled compounds identified a trans-stereoselectivity for the C(sp3 )-H glycosylation. The glycoside C(sp3 )-H activation manifold was likewise exploited for the diversification of furanoses, pyranoses and disaccharides.

Stereoselective gem-C,B-Glycosylation via 1,2-Boronate Migration

A novel protocol is established for the long-standing challenge of stereoselective geminal bisglycosylations of saccharides. The merger of PPh₃ as a traceless glycosidic leaving group and 1,2-boronate migration enables the simultaneous introduction of C-C and C-B bonds at the anomeric stereogenic center of furanoses and pyranoses. The power of this method is showcased by a set of site-selective modifications of glycosylation products for the construction of bioactive conjugates and skeletons. A scarce metal-free 1,1-difunctionalization process of alkenes is also concomitantly demonstrated.

Recent advances in palladium-catalyzed C(sp3)/C(sp2)-H bond functionalizations: access to C-branched glycosides

Over the recent decades, tremendous interest has developed in the transformation of complex substrates by C-H activation and functionalization. In particular, palladium-catalyzed directing and non-directing group-assisted C-H functionalization has emerged as a powerful avenue to access C-branched glycosides. Due to the extreme complexity, delicate functionalities, and high stability of C-H bonds, site-selective functionalization of carbohydrate under mild conditions is highly desirable. The purpose of this review is to cover most of the recent advances in palladium-catalyzed C(sp³) and C(sp²)-H bond functionalizations for the synthesis of C-branched glycosides along with future directions.

Palladium catalyzed decarboxylative β-C-glycosylation of glycals with oxazol-5-(4H)-ones as acceptors

Palladium catalyzed decarboxylative glycosylation of bicyclic glycals affords a series of C-glycosylated oxazol-5-(4H)-ones with high efficiency and exquisite chemo- and stereoselectivity at the anomeric center under mild reaction conditions.

From Amides to Urea Derivatives or Carbamates with Chemospecific C-C Bond Cleavage at Room Temperature

The ureas and carbamates are common motifs in pharmaceuticals, agrochemicals, biologically active compounds and organocatalysis applications. Herein, we report a significant advance in this area and present the general method...

Amine-Directed Mizoroki-Heck Arylation of Free Allylamines

The transition metal-catalyzed Mizoroki−Heck reaction is a powerful method to synthesize C–C bonds, allowing access to several important pharmaceuticals. Traditionally free amines have not been compatible with these approaches due...

Palladium-catalyzed C-H glycosylation and retro Diels-Alder tandem reaction via structurally modified norbornadienes (smNBDs)

This report describes palladium-catalyzed C–H glycosylation and retro Diels–Alder tandem reaction via structurally modified norbornadienes (smNBDs). smNBDs were proposed to regulate the reactivity of the aryl-norbornadiene-palladacycle (ANP), including its high chemoselectivity and regioselectivity, which were the key to constructing C2 and C3 unsubstituted C4-glycosidic indoles. The scope of this substrate is extensive; the halogenated six-membered and five-membered glycosides were applied to the reaction smoothly, and N-alkyl (primary, secondary and tertiary) C4-glycosidic indoles can also be obtained by this method. In terms of mechanism, the key ANP intermediates characterized by X-ray single-crystal diffraction and further controlled experiments proved that the migration-insertion of smNBDs with phenylpalladium intermediate endows them with high chemo- and regioselectivity. Finally, density functional theory (DFT) calculation further verified the rationality of the mechanism.

This report describes palladium-catalyzed C–H glycosylation and retro Diels–Alder tandem reaction via structurally modified norbornadienes (smNBDs).

Highly regioselective and stereoselective synthesis of C-Aryl glycosides via nickel-catalyzed ortho-C-H glycosylation of 8-aminoquinoline benzamides

C-Aryl glycosides are of high value as drug candidates. Here a novel and cost-effective nickel catalyzed ortho-CAr-H glycosylation reaction with high regioselectivity and excellent α-selectivity is described. This method shows great functional group compatibility with various glycosides, showing its synthetic potential. Mechanistic studies indicate that C-H activation could be the rate-determining step.