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Cyclodextrins are widely used as carriers of small molecules for drug delivery owing to their remarkable host properties and excellent biocompatibility. However, cyclic oligosaccharides with different sizes and shapes are limited. Cycloglycosylation of ultra‐large bifunctional saccharide precursors is challenging due to the constrained conformational spaces. Herein we report a promoter‐controlled cycloglycosylation approach for the synthesis of cyclic α‐(1→6)‐linked mannosides up to a 32‐mer. Cycloglycosylation of the bifunctional thioglycosides and (Z)‐ynenoates was found to be highly dependent on the promoters. In particular, a sufficient amount of a gold(I) complex played a key role in the proper preorganization of the ultra‐large cyclic transition state, providing a cyclic 32‐mer polymannoside, which represents the largest synthetic cyclic polysaccharide to date. NMR experiments and a computational study revealed that the cyclic 2‐mer, 4‐mer, 8‐mer, 16‐mer, and 32‐mer mannosides adopted different conformational states and shapes. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Traditional protecting groups are often removed under harsh conditions with potentially hazardous reagents, thereby impeding the convenient synthesis of oligosaccharides and glycosides. Herein, we present to utilize the photolabile ortho‐nitro‐benzyl carbonate (oNBC) as a permanent hydroxyl protecting group for stereocontrolled synthesis of glycosides. The Ph3PO‐modulated glycosylation with strongly disarmed per‐O‐oNBC‐protected glycosyl ynenoates preferred to afford glycosides with excellent α‐selectivities via the β‐phosphonium transition state. Based on the oNBC‐mediated galactosylation, synthesis of the glycolipid digalactosyl diacylglycerol (DGDG) containing six double bonds and two esters was achieved in a straightforward manner. [ABSTRACT FROM AUTHOR]

In their Research Article (e202307851), Peng Xu, Alba Silipo, You Yang et al. present a promoted-controlled cycloglycosylation approach for the synthesis of a series of cyclic mannosides up to a 32-mer. Keywords: Carbohydrates; Conformational Analysis; Cyclic Oligosaccharides; Cycloglycosylation; Glycosylation EN Carbohydrates Conformational Analysis Cyclic Oligosaccharides Cycloglycosylation Glycosylation 1 1 1 10/18/23 20231023 NES 231023 B Cyclic oligosaccharides b such as cyclodextrins are extensively employed as carriers fo drug delivery owing to their remarkable host properties and excellent biocompatibility. Carbohydrates, Conformational Analysis, Cyclic Oligosaccharides, Cycloglycosylation, Glycosylation. [Extracted from the article]

A Ph 3 PO-modulated β-selective Kdo glycosidation approach is developed for the stereoselective synthesis of β-Kdo glycosides. With the readily available per- O -acetylated Kdo ynenoate as the donor, the glycosylation with a series of alcohols in the presence of Ph 3 PAuOTf and Ph 3 PO in toluene at low temperatures afforded the desired Kdo glycosides with good to excellent β-selectivities. Furthermore, the Ph 3 PO-modulated approach was effectively applied to the synthesis of β-(2→4)- and β-(2→8)-linked Kdo-Kdo disaccharides for further biological studies.

Cyclodextrins are widely used as carriers of small molecules for drug delivery owing to their remarkable host properties and excellent biocompatibility. However, cyclic oligosaccharides with different sizes and shapes are limited. Cycloglycosylation of ultra-large bifunctional saccharide precursors is challenging due to the constrained conformational spaces. Herein we report a promoter-controlled cycloglycosylation approach for the synthesis of cyclic α-(1→6)-linked mannosides up to a 32-mer. Cycloglycosylation of the bifunctional thioglycosides and (Z)-ynenoates was found to be highly dependent on the promoters. In particular, a sufficient amount of a gold(I) complex played a key role in the proper preorganization of the ultra-large cyclic transition state, providing a cyclic 32-mer polymannoside, which represents the largest synthetic cyclic polysaccharide to date. NMR experiments and a computational study revealed that the cyclic 2-mer, 4-mer, 8-mer, 16-mer, and 32-mer mannosides adopted different conformational states and shapes., (© 2023 Wiley-VCH GmbH.)