Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Influence of protecting groups on the anomeric equilibrium; case of the 4,6-O-benzylidene acetal in the mannopyranose series.

ABSTRACT: It is reported that the replacement of the 4- and 6-O-benzyl ethers in 2,3,4,6-tetra-O-benzyl-?,?-mannopyranose by a 4,6-O-benzylidene acetal results in an increased population of the ?-anomer at equilibrium in CDCl(3) solution. The phenomenon is considered to arise from the lower steric bulk of the benzylidene acetal that, through diminished buttressing interactions, reduces steric interactions normally present in the ?-anomer.

SUBMITTER: Sharma I

PROVIDER: S-EPMC3396728 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Influence of protecting groups on the anomeric equilibrium; case of the 4,6-O-benzylidene acetal in the mannopyranose series.

Sharma Indrajeet I Bohé Luis L Crich David D

Carbohydrate research 20120607

It is reported that the replacement of the 4- and 6-O-benzyl ethers in 2,3,4,6-tetra-O-benzyl-α,β-mannopyranose by a 4,6-O-benzylidene acetal results in an increased population of the β-anomer at equilibrium in CDCl(3) solution. The phenomenon is considered to arise from the lower steric bulk of the benzylidene acetal that, through diminished buttressing interactions, reduces steric interactions normally present in the β-anomer. ...[more]

PMID: 22739244

Similar Datasets

Probing the influence of protecting groups on the anomeric equilibrium in sialic acid glycosides with the persistent radical effect.

Project description:A method for the investigation of the influence of protecting groups on the anomeric equilibrium in the sialic acid glycosides has been developed on the basis of the equilibration of O-sialyl hydroxylamines by reversible homolytic scission of the glycosidic bond following the dictates of the Fischer-Ingold persistent radical effect. It is found that a trans-fused 4O,5N-oxazolidinone group stabilizes the equatorial glycoside, i.e., reduces the anomeric effect, when compared to the 4O,5N-diacetyl protected systems. This effect is discussed in terms of the powerful electron-withdrawing nature of the oxazolidinone system, which in turn is a function of its strong dipole moment in the mean plane of the pyranose ring system. The new equilibration method displays a small solvent effect and is most pronounced in less polar media consistent with the anomeric effect in general. The unusual (for anomeric radicals) poor kinetic selectivity of anomeric sialyl radicals is discussed in terms of the planar ?-type structure of these radicals and of competing 1,3-diaxial interactions in the diastereomeric transition states for trapping on the ?- and ?-faces of the radical.

| S-EPMC4004215 | biostudies-literature

Influence of the O3 protecting group on stereoselectivity in the preparation of C-mannopyranosides with 4,6-O-benzylidene protected donors.

Project description:?-C-Glucopyranosides and mannopyranosides are obtained in 65-85% yields from 4,6-O-benzylidene-protected glucosyl and mannosyl thioglycosides bearing ester functionality at the 3-O-position by a coupling reaction with C-nucleophiles on activation with diphenyl sulfoxide, 2,4,6-tri-tert-butylpyrimidine, and trifluoromethanesulfonic anhydride.

| S-EPMC3064765 | biostudies-literature

Solvent-controlled regioselective protection of allyl-4,6-benzylidene glucopyranosides.

Project description:We wish to report a simple synthetic procedure, which permits the regiospecific mono-acylation, alkylation and silylation at the 2-position of allyl 4,6-O-benzylidene alpha-D-glucopyranoside in high yields and which does not require the use of catalysts.

| S-EPMC2048501 | biostudies-literature

Removal of benzylidene acetal and benzyl ether in carbohydrate derivatives using triethylsilane and Pd/C.

Project description:Clean deprotection of carbohydrate derivatives containing benzylidene acetals and benzyl ethers was achieved under catalytic transfer hydrogenation conditions by using a combination of triethylsilane and 10% Pd/C in CH(3)OH at room temperature. A variety of carbohydrate diol derivatives were prepared from their benzylidene derivatives in excellent yield.

| S-EPMC3566760 | biostudies-literature

Combinatorial Library of Cyclic Benzylidene Acetal-Containing pH-Responsive Lipidoid Nanoparticles for Intracellular mRNA Delivery.

Project description:Lipidoid nanoparticles have been demonstrated to be effective for intracellular delivery of small molecule drugs, proteins, and nucleic acids. Stimuli-responsive lipidoid nanoparticles are able to further improve delivery efficacy and reduce carrier-induced toxicity. Our group previously developed reduction and photoresponsive combinatorial libraries of lipidoid nanoparticles for small molecule and biologics delivery. Herein, we describe the synthesis, characterization, and intracellular mRNA delivery application of a new library of pH-responsive lipidoid nanoparticles. The acid-degradable cyclic benzylidene acetal-containing cationic lipidoids (R-O16CBA) were synthesized through a multistep reaction and characterized by NMR and MS. The acid-triggered degradation of lipidoids was studied using NMR, MS, DLS, and TEM. The results revealed that the R-O16CBA lipidoid can be completely degraded at pH 5. The R-O16CBA lipidoid nanoparticles were then fabricated with different formulations of DOPE and cholesterol and tested in vitro for intracellular mRNA delivery.

| S-EPMC9069324 | biostudies-literature

On the influence of the C2-O2 and C3-O3 bonds in 4,6-O-benzylidene-directed beta-mannopyranosylation and alpha-glucopyranosylation.

Project description:The synthesis of 4,6-O-benzylidene-protected 2-deoxyarabino-, 3-deoxyarabino-, and 3-deoxyribothioglycosides is described and their glycosylation reactions, with activation by either 1-benzenesulfinyl piperidine/trifluoromethansulfonic anhydride or diphenyl sulfoxide/trifluoromethanesulfonic anhydride, studied. In contrast to the corresponding 4,6-O-benzylidene-protected glucosyl and mannosyl donors, which are alpha- and beta-selective, respectively, poor diastereoselectivity is observed in all cases. The reasons for this poor selectivity are discussed in terms of the interaction between the C2-O2 and C3-O3 bonds in the glucosyl and mannosyl donors and of the influence of this interaction on the ease of formation of the intermediate glycosyl oxacarbenium ions.

| S-EPMC2621314 | biostudies-literature

Development of Anhydrous Ethanol Purification: Reduction of Acetal Content and Vapor-Liquid Equilibrium Study of the Ethanol-Acetal Binary System.

Project description:Acetaldehyde diethyl acetal (herein called acetal) is an important pollutant of anhydrous ethanol. Isobaric vapor-liquid equilibrium (VLE) of an ethanol-acetal binary system was measured using a vapor condensate and liquid circulation VLE still. The experimental data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, which were found suitable for representing the VLE data. Proper agreements between experimental and calculated VLE data were obtained, which were then confirmed with consistency tests. The applicability of the novel VLE data was demonstrated during an investigation of an anhydrous ethanol purification column. Reduction of the concentration of acetal and other pollutants was examined and optimized in a flowsheet environment. The modeling results were verified in a laboratory with an experimental distillation column, confirming a correct agreement between the results. It must be highlighted that the developed method is suitable for the production of pharmacopeial quality anhydrous alcohol, based on reliable, verified VLE data. The results show the importance of accurate VLE data in critical compositions (low pollutant content); moreover, aiming at high product purity, experimental validation has paramount importance. The consistency between the three platforms (VLE and distillation experiments and flowsheet simulation) confirms the accuracy of the developed method.

| S-EPMC7818642 | biostudies-literature

Probing the influence of a 4,6-O-acetal on the reactivity of galactopyranosyl donors: verification of the disarming influence of the trans-gauche conformation of C5-C6 bonds.

Project description:The effect of a 4,6-O-alkylidene acetal on the rate of acid-catalyzed hydrolysis of methyl galactopyranosides and of spontaneous hydrolysis of 2,4-dinitrophenyl galactopyranosides has been studied through the synthesis and hydrolysis of analogs in which O6 is replaced by a methoxymethylene unit in which the methoxy group adopts either an equatorial or an axial position according to the configuration. Consistent with earlier studies under both acid-catalyzed and spontaneous hydrolysis conditions, the alkylidene acetal, or its 7-carba analog, retards hydrolysis with respect to comparable systems lacking the cyclic protecting group. The configuration at C6 in the 7-carba analogs does not influence the rate of acid-catalyzed hydrolysis but has a minor influence on the rate of spontaneous hydrolysis of the 2,4-dinitrophenyl galactosides, confirming earlier studies on the role played by the hydroxymethyl group conformation on glycoside reactivity. The benzylidene acetal is found to stabilize the ?-anomer of galactopyranose derivatives relative to monocyclic analogs. Reasons for the ?-selectivity of 4,6-O-benzylidene-protected galactopyranosyl donors bearing neighboring group-active protecting groups at O2 are discussed.

| S-EPMC3814037 | biostudies-literature

Influence of protecting groups on O- and C-glycosylation with neuraminyl and ulosonyl dibutylphosphates.

Project description:The adamantanyl thioglycosides of 5-isothiocyano and 5-azido 5-desamino-4,7,8,9-tetra-O-acetylneuraminic acid methyl ester were converted into the corresponding dibutyl phosphates, which proved to be excellent α-selective donors for O-sialidation with a range of typical acceptors, and good donors for reaction with allyltributylstannane, albeit without significant anomeric selectivity. In the KDN series the dibuylphosphate derived from a donor carrying a 4,5-cyclic carbonate protecting group afforded the corresponding C-glycoside with excellent α-selectivity on activation in the presence of allyltributylstannane, whereas the corresponding donor carrying acetate esters at the 4- and 5-positions was unselective. Overall, it is revealed that while the strongly electron-withdrawing isothiocyanato and azido groups are sufficient to promote highly α-selective O-sialidation, they are inadequate when faced with less reactive nucleophiles when mixtures of anomers are obtained.

| S-EPMC7484008 | biostudies-literature

Automated Glycan Assembly of Oligogalactofuranosides Reveals the Influence of Protecting Groups on Oligosaccharide Stability.

Project description:Galactofurans are an important structural constituent of arabinogalactan and lipopolysaccharides (LPS) ubiquitously present on the envelopes of all Mycobacteria. Key to the automated glycan assembly (AGA) of linear galactofuranosides as long as 20-mers was the identification of thioglycoside building blocks with a fine balance of stereoelectronic and steric effects to ensure the stability of oligogalactofuranoside during the synthesis. A benzoylated galactofuranose thioglycoside building block proved most efficient for oligosaccharide construction.

| S-EPMC8154612 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data