Browse
Submit Data
Databases
API
Help

Dataset Information

14 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

An Improved Helferich Method for the α/β-Stereoselective Synthesis of 4-Methylumbelliferyl Glycosides for the Detection of Microorganisms.

ABSTRACT: An improved Helferich method is presented. It involves the glycosylation of 4-methyl-umbelliferone with glycosyl acetates in the presence of boron trifluoride etherate combined with triethylamine, pyridine, or 4-dimethylaminopyridine under mild conditions, followed by deprotection to give fluorogenic 4-methylumbelliferyl glycoside substrates. Due to the use of base, the glycosylation reaction proceeds more easily, is uncommonly α- or β-stereoselective, and affords the corresponding products in moderate to excellent yields (51%-94%) under appropriate conditions.

SUBMITTER: Wei X

PROVIDER: S-EPMC6331929 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Stereoselective synthesis of 2-deoxy-beta-glycosides using anomeric O-alkylation/arylation.

Project description:Anomeric O-alkylation/arylation is applied to the synthesis of 2-deoxy-beta-glycosides. Treatment of lactols with NaH in dioxane followed by the addition of electrophiles leads to the formation of 2-deoxy-beta-glycosides in high yield and high selectivity. The high beta-selectivity observed here demonstrates a powerful stereoelectronic effect for the stereoselective formation of acetals under kinetic control.

| S-EPMC2699938 | biostudies-literature

Stereoselective Synthesis of the Equatorial Glycosides of Legionaminic Acid.

Project description:The synthesis of a legionaminic acid donor from N-acetylneuraminic acid in 15 steps and 17% overall yield is described. Activation of the adamantanyl thioglycoside in the donor with N-iodosuccinimide and trifluoromethanesulfonic acid in dichloromethane and acetonitrile at -78 °C in the presence of primary, secondary and tertiary alcohols affords the corresponding glycosides in excellent yield and good to excellent equatorial selectivity. In particular, coupling to the 4-OH of a suitably protected neuraminic acid derivative affords a disaccharide that closely resembles the glycosidic linkage in the polylegionaminic acid from the lipopolysaccharide of the Legionella pneumophila virulence factor. A straightforward deprotection sequence enables conversion of the protected glycosides to the free N,N-diacetyllegionaminic acid glycosides.

| S-EPMC5545936 | biostudies-literature

Stereoselective synthesis of alpha,alpha'-biprolines.

Project description:A means to induce dehydrodimerization of Seebach's oxazolidinone (5), the stereochemical outcome of which is entirely temperature dependent, is described. The resultant dimers 3 and 4 are precursors to (R,R)-alpha,alpha'-biproline (1) and meso-alpha,alpha'-biproline (2), respectively. An organohypobromite and an iminium halide are proposed to serve as electrophiles in the reaction with the enolate of 5 to give 3 and 4, respectively.

| S-EPMC1388272 | biostudies-literature

Engineering Thermotoga maritima β-glucosidase for improved alkyl glycosides synthesis by site-directed mutagenesis.

Project description:Alkyl glycosides are well-characterized nonionic surfactants, and can be prepared by transglycosylation reactions with retaining GH1 glycosidases being normally used for this purpose. The produced alkyl glycosides can also be hydrolyzed by the glycosidase, and hence, the yields of alkyl glycosides can be too low for industrial use. To improve the transglycosylation-to-hydrolysis ratio for a β-glucosidase from Thermotoga maritima (TmBglA) for the synthesis of alkyl glycoside, six mutants (N222F, N223C, N223Q, G224A, Y295F, and F414S) were produced. N222F, N223C, N223Q, G224A improved catalytic activity, F295Y and F414S are hydrolytically crippled with p-nitrophenol-β-d-glucopyranoside (pNPG) as substrate with an 85 and 70-fold decrease in apparent kcat, respectively; N222F shows the highest kcat/km value for pNPG. The substrate selectivity altered from pNPG to pNP-β-d-fucoside for N222F, F295Y, and F414S and from cellubiose to gentiobiose for N222F and F414S. Using pNPG (34 mM) and hexanol 80% (vol/vol), N222F, Y295F, and F414S synthesized hexyl-β-glycoside (HG) yields of 84.7%, 50.9%, and 54.1%, respectively, HG increased from 14.49 (TmBglA) to 22.8 mM (N222F) at 2 hr by 57.42%. However, this higher transglycosylation effect depended on that three mutants creates an environment more suited for hexanol in the active site pocket, and consequently suppressed its HG hydrolysis.

| S-EPMC9113129 | biostudies-literature

Stereoselective Synthesis of β-Branched Aromatic α-Amino Acids by Biocatalytic Dynamic Kinetic Resolution*.

Project description:β-Branched noncanonical amino acids are valuable molecules in modern drug development efforts. However, they are still challenging to prepare due to the need to set multiple stereocenters in a stereoselective fashion, and contemporary methods for the synthesis of such compounds often rely on the use of rare-transition-metal catalysts with designer ligands. Herein, we report a highly diastereo- and enantioselective biocatalytic transamination method to prepare a broad range of aromatic β-branched α-amino acids. Mechanistic studies show that the transformation proceeds through dynamic kinetic resolution that is unique to the optimal enzyme. To highlight its utility and practicality, the biocatalytic reaction was applied to the synthesis of several sp3 -rich cyclic fragments and the first total synthesis of jomthonic acid A.

| S-EPMC8319157 | biostudies-literature

Stereoselective esterase from Pseudomonas putida IFO12996 reveals alpha/beta hydrolase folds for D-beta-acetylthioisobutyric acid synthesis.

Project description:Esterase (EST) from Pseudomonas putida IFO12996 catalyzes the stereoselective hydrolysis of methyl dl-beta-acetylthioisobutyrate (dl-MATI) to produce d-beta-acetylthioisobutyric acid (DAT), serving as a key intermediate for the synthesis of angiotensin-converting enzyme inhibitors. The EST gene was cloned and expressed in Escherichia coli; the recombinant protein is a non-disulfide-linked homotrimer with a monomer molecular weight of 33,000 in both solution and crystalline states, indicating that these ESTs function as trimers. EST hydrolyzed dl-MATI to produce DAT with a degree of conversion of 49.5% and an enantiomeric excess value of 97.2% at an optimum pH of about 8 to 10 and an optimum temperature of about 57 to 67 degrees C. The crystal structure of EST has been determined by X-ray diffraction to a resolution of 1.6 A, confirming that EST is a member of the alpha/beta hydrolase fold superfamily of enzymes and includes a catalytic triad of Ser97, Asp227, and His256. The active site is located approximately in the middle of the molecule at the end of a pocket approximately 12 A deep. EST can hydrolyze the methyl ester group without affecting the acetylthiol ester moiety in dl-MATI. The examination of substrate specificity of EST toward other linear esters revealed that the enzyme showed specific activity toward methyl esters and that it recognized the configuration at C-2.

| S-EPMC1317000 | biostudies-literature

Stereoselective Synthesis of β-Glycinamide Ribonucleotide.

Project description:A diastereoselective synthesis of the β-anomer of glycinamide ribonucleotide (β-GAR) has been developed. The synthesis was accomplished in nine steps from D-ribose and occurred in 5% overall yield. The route provided material on the multi-milligram scale. The synthetic β-GAR formed was remarkably resistant to anomerization both in solution and as a solid.

| S-EPMC9024515 | biostudies-literature

Reagent Controlled Stereoselective Synthesis of α-Glucans.

Project description:The development of a general glycosylation method that allows for the stereoselective construction of glycosidic linkages is a tremendous challenge. Because of the differences in steric and electronic properties of the building blocks used, the outcome of a glycosylation reaction can vary greatly when switching form one glycosyl donor-acceptor pair to another. We here report a strategy to install cis-glucosidic linkages in a fully stereoselective fashion that is under direct control of the reagents used to activate a single type of donor building block. The activating reagents are tuned to the intrinsic reactivity of the acceptor alcohol to match the reactivity of the glycosylating agent with the reactivity of the incoming nucleophile. A protecting group strategy is introduced that is based on the sole use of benzyl-ether type protecting groups to circumvent changes in reactivity as a result of the protecting groups. For the stereoselective construction of the α-glucosyl linkages to a secondary alcohol, a per-benzylated glusosyl imidate donor is activated with a combination of trimethylsilyltriflate and DMF, while activation of the same imidate donor with trimethylsilyl iodide in the presence of triphenylphosphine oxide allows for the stereoselective cis-glucosylation of primary alcohols. The effectiveness of the strategy is illustrated in the modular synthesis of a Mycobacterium tuberculosis nonasaccharide, composed of an α-(1-4)-oligoglucose backbone bearing different α-glucosyl branches.

| S-EPMC5890317 | biostudies-literature

A highly stereoselective synthesis of chiral alpha-amino-beta-lactams via the Kinugasa reaction employing ynamides.

Project description:A highly stereoselective synthesis of chiral alpha-amino-beta-lactam through an ynamide-Kinugasa reaction is described. In addition, a mechanistic model is illustrated here to rationalize the observed diastereoselectivity, which depends on both the initial [3 + 2] cycloaddition step and the subsequent protonation for which both are highly selective.

| S-EPMC2587087 | biostudies-literature

Stereoselective synthesis of highly functionalized alpha-diazo-beta-ketoalkanoates via catalytic one-pot Mukaiyama-Aldol reactions.

Project description:Methyl diazoacetoacetate undergoes zinc triflate catalyzed condensation with a broad selection of aldehydes to produce delta-siloxy-alpha-diazo-beta-ketoalkanoates in good yield, and delta-hydroxy-alpha-diazo-beta-ketoalkanoates are formed with high diastereoselectivity in reactions with alpha-diazo-beta-ketopentanoate promoted by dibutylboron triflate.

| S-EPMC2829718 | 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