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We describe the synthesis of the first heteroglycoclusters featuring three distinct carbohydrate ligands. The obtained pair of stereoisomeric glycoclusters were named "focal point enantiomers", as the configuration of the focal point is the only varying stereogenic element in these molecules. The first pair of such diastereomeric heteroglycoclusters was accessible by an efficient sequence of protection and sequential glycosylation steps utilizing a mannosyl, a N‐acetylglucosaminyl, and a galactosyl donor, respectively, which was applied to a prototype azido‐functionalized tris(hydroxymethyl)aminomethane (TRIS) scaffold molecule. The stereoisomers could be distinguished based on an X‐ray structure of one of the isomeric key intermediates. As previously shown with divalent counterparts, such heterotrivalent cluster glycosides are useful tools for studying the fine‐tuning of carbohydrate recognition. The azido functional group at the focal point of the synthetic scaffold molecule was employed in a conjugation reaction with a linker for further immobilization on a gold surface in order to fabricate glyco‐SAMs (self‐assembled monolayers). A preliminary biological evaluation of the focal point enantiomers was performed in solution using the well‐known model lectin Concanavalin A and the important bacterial lectin FimH. [ABSTRACT FROM AUTHOR]

para‐Nitrophenyl (PNP) ethers of glycosides are important building blocks en route to functional carbohydrates. They are stable in neutral media, however, under basic conditions such as during the Zemplén deacylation of sugars, aryl migration is frequently observed. We have employed a library of O‐PNP‐substituted methyl glycosides of the manno‐, galacto‐, gluco‐ and altro‐series to study the kinetics of aryl migration in MeOH/sodium methoxide using NMR spectroscopy revealing that migration between cis‐oriented OH groups is faster than between trans‐oriented ones. The rate constants of migration decrease in the order of Alt>Man>Gal>Glc and are related to the energy barriers of chair conformation inversion. The energy profile of the 3 to 4‐PNP migration in methyl mannoside was calculated using DFT methods suggesting the Meisenheimer complex is an intermediate of PNP migration and that coordination of the sodium cation has a major impact on the energy profile. [ABSTRACT FROM AUTHOR]

Carbohydrate recognition is essential for numerous biological processes and is governed by various factors within the supramolecular environment of the cell. Photoswitchable glycoconjugates have proven as valuable tools for the investigation and modulation of carbohydrate recognition as they allow to control the relative orientation of sugar ligands by light. In order to advance the possibilities of such an "optoglycomics" approach for the glycosciences, we have synthesized a biantennary glycocluster in which two glycoazobenzene antennas are conjugated to the 3‐ and 6‐position of a scaffold glycoside. Orthogonal isomerization of the photoswitchable units was made possible by the different conjugation of the azobenzene moieties via an oxygen and a sulfur atom, respectively, and the ortho‐fluorination of one of the azobenzene units. This design enabled a switching cycle comprising the EE, EZ and the ZZ isomer. This is the first example of an orthogonally photoswitchable glycocluster. The full analysis of its photochromic properties included the investigation of the isolated glycoazobenzene antennas allowing the comparison of the intra‐ versus the intermolecular orthogonal photoswitching. The kinetics of the thermal relaxation were analyzed in detail. A molecular dynamics study shows that indeed, the relative orientation of the glycoantennas and the distances between the terminal sugar ligands significantly vary depending on the isomeric state, as intended. [ABSTRACT FROM AUTHOR]

The article in Chemistry - A European Journal explores the migration of para-nitrophenyl groups in methyl pyranosides, showcasing a race between different sugars to transfer the substituent from start to finish. The rate constants of the migration are depicted by animals and a stone, with the track featuring a bump symbolizing the energy barrier. The research investigates PNP migration for various sugars, providing insights into rate constants, energy barriers, and theoretical studies on the mechanism and its energetic profile. For more details, readers can refer to the Research Article by Friedrich, Lütjohann, Hartke, and Lindhorst. [Extracted from the article]

Research has been conducted on the oligosaccharide mimetics. Results indicate that the syntheses of these mimetics can occur via the synthesis of the trifunctional glycoside used as a scaffold for the attachment of monosaccharide derivatives to the di-, tri- and tetrasaccharide mimetics.

Two synthetic strategies, the monosaccharide pathway and the trehalose pathway, for synthesizing selectively functionalized cluster glycosides, glycocluster are described. The amino-functionalized aglycone in the glycocluster serves as a tether for further synthesis of compound biotinylated cluster.