Regio- and Stereoselective C-Glycosylation of Indoles Using o-[1-(p-MeO-Phenyl)vinyl]benzoates (PMPVB) as Glycosyl Donors under Brønsted Acid Catalysis

Efficient synthesis of indole-chalcones based glycohybrids and their anticancer activity

Indole based glycosides belong to the class of pharmacologically active molecules and found in diverse natural compounds. Herein, we report the synthesis of 1,2,3-triazole bridged chirally enriched diverse indole-chalcones based glycohybrids. Three series of glycohybrids were designed and efficiently synthesized using d-glucose, d-galactose and d-mannose derived 1-azido glycosides. The reactions sequence involved were, the synthesis of indole derived chalcones which were formed via Claisen-Schmidt condensation reaction and subsequently N-propargylation which leads to the production of N-propargylated indole-chalcones. The N-propargylated indole-chalcones get transformed into 1,2,3-triazole bridged indole-chalcone based glycohybrids by reacting with 1-azido sugar glycosides under click-chemistry reaction conditions. Further, the biological activity of synthesized glycohybrids (n = 27) was assessed in-vitro against MDA-MB231, MCF-7, MDA-MB453 cancer, and MCF-10A normal cell lines. The selected compounds showed potent anti-oncogenic properties against MCF-7 and MDA-MB231 breast cancer cell line with IC50 values of 1.05 µM and 11.40 µM respectively, with very good selectivity index (SI > 161). The active compounds show better binding affinity as compared to co-crystallized inhibitor 1-(tert-butyl)-3-(p-tolyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine (PP1) with HCK (PTKs) proteins in molecular docking studies.

Triple Role of Proton Sponge (DMAN) in the Palladium-Catalyzed Direct Stereoselective Synthesis of C-Aryl Glycosides from Glycals

The triple role of 1,8-bis(dimethylamino)naphthalene (proton sponge) as a reductant, ligand precursor, and organic base in the palladium-catalyzed Heck-type coupling reaction of glycals with aryl iodides affords the rapid and stereoselective synthesis of 2',3'-unsaturated α-C-aryl glycosides in excellent yields. The role of the proton sponge in reducing palladium(II) to (0) has been studied using cyclic voltammetry, UV-vis, HRMS, and other spectroscopic techniques. This is the first example of a palladium proton sponge complex utilized in coupling reactions. The method is observed to be tolerant of various functional groups, as demonstrated by the huge substrate scope. Moreover, the 2',3'-unsaturated α-C-aryl glycosides were also converted to 3-keto-β-C-glycosides under sterically hindered pyridinium salt catalysis via a ring-opening and -closing mechanism.

Recent progress in the synthesis of natural product inspired bioactive glycohybrids

Carbohydrates are a basic structural component that are indispensable to all cellular processes. In addition to being employed as chiral starting materials in the synthesis of a variety of natural products, carbohydrates are recognized as naturally occurring molecules having an enormous variety of functional, stereochemical, and structural properties. The understanding and biological roles of carbohydrate derived molecules can be greatly improved by selectively synthesizing functional carbohydrates through incorporating them with privileged scaffolds. For a deeper understanding of their roles and the development of functional materials based on sugar, it is crucial to develop new techniques for efficiently synthesizing, functionalizing, and modifying carbohydrates. Glycohybrids have a wide range of structural and functional characteristics along with protein-carbohydrate interactions that are crucial to mammalian biology and a number of disease states. This review, consisting the literature from January 2017 to July 2023 and provide an overview of recent developments in the chemical synthesis of glycohybrids based on natural product scaffolds of coumarin, quinolone, naphthalene diimide, indole, isatin, naphthoquinone, imidazole and pyrimidine. The biological activity of active glycohybrids are discussed in this review.

Stereoselective Synthesis of Indolyl-C-glycosides Enabled by Sequential Aminopalladation and Heck Glycosylation of 2-Alkynylanilines with Glycals

An efficient and general approach for the synthesis of indolyl-C-glycosides via aminopalladation and subsequent Heck-type glycosylation of easily available 2-alkynylanilines and glycals has been developed. This protocol features excellent stereoselectivity, a broad substrate scope, and mild reaction conditions. In addition, 2,3-pseudoglycals also successfully participated in this cascade reaction, affording C2/C3-branched indolyl glycosides with high regio-/stereoselectivity. The utility of this protocol was also demonstrated by a large-scale reaction and diversified synthetic transformations of the desired products.

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-C-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 C-glycosylation while unexpectedly driving the anomerization of α-anomers through endocyclic cleavage of the C1-O5 bond, resulting in the formation of β-C-deoxyglycosides. Furthermore, density functional theory (DFT) calculations shed light on the reaction mechanism, emphasizing the significant role of the pyridine group of indole in stabilizing transition states and intermediates.