Palladium(ii)-catalyzed stereoselective synthesis of C-glycosides from glycals with diaryliodonium salts

Glycals as Chiral Synthons in Organic Synthesis of Privileged Molecular Scaffolds

Chirality is a vital characteristic of molecules and crucial for biological functioning. Glycals are unsaturated chiral sugars that contain an enolic double bond within the ring structure and they introduce the chirality in the molecular scaffolds. Since their discovery and synthesis by Fischer and Zach in 1913, they have been used as a flexible chiral synthon for synthesising natural products and biologically significant molecules. An important area of study in organic synthesis involves functionalizing glycals, with particular emphasis on creating novel molecular scaffolds with a common backbone using various topologies. This review discusses recent advancements in synthesizing chiral molecules, emphasizing the innovative use of glycals as chiral synthons, and covers literature from 2020 to the present.

Stereoselective Synthesis of Glycosides via Tsuji-Trost Type Glycosylation Using 3,4-Carbonate Galactals

Pd-catalyzed stereoselective glycosylations using unsaturated sugar derivatives, glycals, have been successfully achieved in recent years. This review focuses on approaches to control the stereoselectivities of glycosides via π-allyl intermediates that mimic the Tsuji-Trost asymmetric allylic alkylation reactions, enabling stereoselectivity control through rational design. In the reaction process, zwitterionic Pd-π-allyl complexes, formed after the oxidative addition and decarboxylation, play a crucial role in increasing reactivities and enhancing the stereoselectivities of α- and β-glycosides. We summarized recently developed Tsuji-Trost type glycosylations using 3,4-carbonate galactals, featuring high efficiency, exclusive stereoselectivities, and a broad reaction scope including O-, N-, S-, and C-glycosylations.

Advancing carbohydrate functionality: The role of hypervalent iodine

Hypervalent iodine reagents have undergone significant development and widespread application in the functionalization of carbohydrates. This is primarily attributed to their exceptional properties, including mildness, ease of handling, high selectivity, environmental friendliness, and stability. This review aims to emphasize the utilization of hypervalent iodine compounds in the functionalization of carbohydrates. The present article covers various aspects, including glycal functionalization, C-H or N-H insertion reactions, O-arylations, C-2 deoxy-2-iodo glycoconjugates, iminosugars, and C3-oxo-glycals, achieved through the use of hypervalent iodine reagents/catalysts. Additionally, it explores hypervalent iodine-mediated bioactive 1,3,5-trioxocane synthesis followed by rare sugars synthesis.

Hypervalent Iodine Compounds in Carbohydrate Chemistry: Glycosylation, Functionalization and Oxidation

This mini review article provides an overview on the use of hypervalent iodine compounds (HICs) in carbohydrate synthesis, focusing on their chemistry and recent applications. HICs are similar to transition metals in their reactivity but have the added benefit of being environmentally benign, and are therefore commonly used as selective oxidants and eco-friendly reagents in organic synthesis. Herein, we summarize various synthetic uses of hypervalent iodine reagents in reactions such as glycosylation, oxidations, functionalization, and C-C bond-forming reactions. The goal of this review is to illustrate the advantages and versatility of using HICs as an environmentally sustainable alternative to heavy metals in carbohydrate chemistry.

Late-stage modification of peptides and proteins at cysteine with diaryliodonium salts

The modification of peptides and proteins has emerged as a powerful means to efficiently prepare high value bioconjugates for a range of applications in chemical biology and for the development of next-generation therapeutics. Herein, we report a novel method for the chemoselective late-stage modification of peptides and proteins at cysteine in aqueous buffer with suitably functionalised diaryliodonium salts, furnishing stable thioether-linked synthetic conjugates. The power of this new platform is showcased through the late-stage modification of the affibody zEGFR and the histone protein H2A.