Mechanism of C-3 Acyl Neighboring Group Participation in Mannuronic Acid Glycosyl Donors DOI Creative Commons
Frank F. J. de Kleijne, Peter H. Moons,

Floor ter Braak

et al.

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 147(1), P. 932 - 944

Published: Dec. 18, 2024

One of the main challenges in oligosaccharide synthesis is stereoselective introduction glycosidic bond. In order to understand and control glycosylation reactions, thorough mechanistic studies are required. Reaction intermediates found by NMR spectroscopy often cannot explain glycosylation's stereochemical outcome. Hence, reactions may proceed through low-abundance reaction that difficult detect, according a Curtin–Hammett scenario. We have previously observed manno-type sugars can engage C-3 acyl neighboring group participation. Herein, we report detection glycosyl dioxanium ions result from participation mannuronic acid donors. Using suite exchange techniques, were able dissect kinetics conformational ring-flip precedes event itself various sugars. this study provides complete picture mannosyl ion formation.

Language: Английский

Elucidating reactive sugar-intermediates by mass spectrometry DOI Creative Commons
Chun‐Wei Chang, Dana Wehner, Gurpur Rakesh D. Prabhu

et al.

Communications Chemistry, Journal Year: 2025, Volume and Issue: 8(1)

Published: March 7, 2025

The stereoselective introduction of glycosidic bonds is one the greatest challenges in carbohydrate chemistry. A key aspect controlling glycan synthesis glycosylation reaction which linkages are formed. outcome governed by a reactive sugar intermediate - glycosyl cation. Glycosyl cations highly unstable and short-lived, making them difficult to study using established analytical tools. However, mass-spectrometry-based techniques perfectly suited unravel structure gas phase. main approach involves isolating intermediate, free from external influences such as solvents promoters. Isolation allows examining their integrating orthogonal spectrometric spectroscopic technologies. In this perspective, recent achievements gas-phase research on highlighted. It provides an overview used probe methods for interpreting spectra. connections between data mechanisms solution explored, given that reactions typically performed solution.

Language: Английский

Citations

0
4,6‐O‐Phenylboronic Ester Protection for 1,2‐cis‐α‐Selective Glucosylation DOI Creative Commons

Yutaka Umemura,

Taro Udagawa, Naoko Komura

et al.

Asian Journal of Organic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: May 23, 2025

Abstract 1,2‐ cis ‐α‐Selective glucosylation is highly desirable for synthesis of naturally occurring, biologically important α‐glucosides; however, its implementation remains challenging due to the absence conventional neighboring group participation. In this study, we reinvestigated α‐glucosylation using 4,6‐ O ‐phenylboronic ester‐protected thioglycoside donor, originally reported by Crich and coworkers in 2003. We report that methyl trifluoromethanesulfonate promoted glucosyl 2‐azido‐2‐deoxyglucosyl donors CH 2 Cl under reflux conditions, achieving good excellent α‐selectivity (up α/β = >20/1). Notably, stereodirecting effect ester protection was greater than 4,6‐benzylidene protection. Mechanistic insight into origin glucosylation, obtained from substrate scope results density function theory calculations, proposed an S N 1 pathway via formation unprecedented borate‐type oxocarbenium intermediate favoring α‐selective nucleophilic attack. The phenyl boronic protecting can be readily quantitatively removed phase‐switching aqueous workup 1.0 m solution d ‐sorbitol Na CO 3 after glucosylation.

Language: Английский

Citations

0
Direct Experimental Characterization of a Sialyl Cation DOI Creative Commons
Franziska Dahlmann, Caleb E. Griesbach, América Y. Torres‐Boy

et al.

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 5, 2024

Abstract Sialic acids are monosaccharide residues involved in several biological processes. Controlling the stereoselectivity of sialylation reactions is challenging and mechanistic studies on structure its intermediate, sialyl cation, scarce. Here it shown that a cation can be generated isolated from an ionized sialic acid precursor. This short‐lived species structurally characterized for first time using cryogenic infrared spectroscopy. In combination with quantum chemical calculations, results reveal positive charge at anomeric carbon stabilized by remote participation C5‐NHAc group leading to formation bridged structure. this structure, β‐side shielded nucleophilic attack, potentially explaining α‐selectivity building block S N 1‐type reactions. Other modes energetically unfavored cannot observed experimentally.

Language: Английский

Citations

1
Mechanism of C-3 Acyl Neighboring Group Participation in Mannuronic Acid Glycosyl Donors DOI Creative Commons
Frank F. J. de Kleijne, Peter H. Moons,

Floor ter Braak

et al.

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 147(1), P. 932 - 944

Published: Dec. 18, 2024

One of the main challenges in oligosaccharide synthesis is stereoselective introduction glycosidic bond. In order to understand and control glycosylation reactions, thorough mechanistic studies are required. Reaction intermediates found by NMR spectroscopy often cannot explain glycosylation's stereochemical outcome. Hence, reactions may proceed through low-abundance reaction that difficult detect, according a Curtin–Hammett scenario. We have previously observed manno-type sugars can engage C-3 acyl neighboring group participation. Herein, we report detection glycosyl dioxanium ions result from participation mannuronic acid donors. Using suite exchange techniques, were able dissect kinetics conformational ring-flip precedes event itself various sugars. this study provides complete picture mannosyl ion formation.

Language: Английский

Citations

1