scholarly journals Boric Acid Catalyzed Methyl Esterification of Sugar Acids

2014 ◽  
Vol 67 (3) ◽  
pp. 528 ◽  
Author(s):  
Stephan M. Levonis ◽  
Brighid B. Pappin ◽  
Alissa Sharp ◽  
Milton J. Kiefel ◽  
Todd A. Houston
Keyword(s):  
Natural Products ◽  
Sialic Acid ◽  
Boric Acid ◽  
Glucuronic Acid ◽  
Quinic Acid ◽  
Neuraminic Acid ◽  
Methyl Esterification ◽  
Acid Catalyzed ◽  
Ulosonic Acid

Boric acid catalyzes methyl esterification of certain sugar acids (sialic acid, deaminated neuraminic acid) and related natural products (quinic acid) quite cleanly in some cases. However, closely related sugar acids (glucuronic acid, 3-deoxy-d-manno-oct-2-ulosonic acid) failed to esterify under the same conditions. Factors governing this dichotomy are discussed.

Synthesis of 1,3,4-trisubstituted pyrrolidines as meropenem adjuvants targeting New Delhi metallo-β-lactamase

2021 ◽  
Vol 45 (7) ◽  
pp. 3515-3534
Author(s):  
Wen Bin Jin ◽  
Chen Xu ◽  
Xiao Lin Qi ◽  
Ping Zeng ◽  
Wei Gao ◽  
...  
Keyword(s):  
Boric Acid ◽  
Dipolar Cycloaddition ◽  
New Delhi ◽  
Acid Catalyzed

A promising NDM-1 inhibitor was discovered by the construction of pyrrolidine library via boric acid-catalyzed 1,3-dipolar cycloaddition and cell-based screens.

Boric acid catalyzed thia-Michael reactions in water or alcohols

2007 ◽  
Vol 269 (1-2) ◽  
pp. 214-217 ◽  
Author(s):  
Mihir K. Chaudhuri ◽  
Sahid Hussain
Keyword(s):  
Boric Acid ◽  
Michael Reactions ◽  
Acid Catalyzed

Boric acid catalyzed Tishchenko reactions

1973 ◽  
Vol 38 (7) ◽  
pp. 1433-1434 ◽  
Author(s):  
Paul R. Stapp
Keyword(s):  
Boric Acid ◽  
Acid Catalyzed

scholarly journals Designing and Development of FRET-Based Nanosensor for Real Time Analysis of N-Acetyl-5-Neuraminic Acid in Living Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Ruphi Naz ◽  
Mohammad K. Okla ◽  
Urooj Fatima ◽  
Mohd. Mohsin ◽  
Walid H. Soufan ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Metabolic Engineering ◽  
Sialic Acid ◽  
Real Time ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Neuraminic Acid ◽  
Yeast Cells ◽  
Metabolite Level ◽  
Health Maintenance

N-acetyl-5-neuraminic acid (NeuAc) plays crucial role in improving the growth, brain development, brain health maintenance, and immunity enhancement of infants. Commercially, it is used in the production of antiviral drugs, infant milk formulas, cosmetics, dietary supplements, and pharmaceutical products. Because of the rapidly increasing demand, metabolic engineering approach has attracted increasing attention for NeuAc biosynthesis. However, knowledge of metabolite flux in biosynthetic pathways is one of the major challenges in the practice of metabolic engineering. So, an understanding of the flux of NeuAc is needed to determine its cellular level at real time. The analysis of the flux can only be performed using a tool that has the capacity to measure metabolite level in cells without affecting other metabolic processes. A Fluorescence Resonance Energy Transfer (FRET)-based genetically-encoded nanosensor has been generated in this study to monitor the level of NeuAc in prokaryotic and eukaryotic cells. Sialic acid periplasmic binding protein (SiaP) from Haemophilus influenzae was exploited as a sensory element for the generation of nanosensor. The enhanced cyan fluorescent protein (ECFP) and Venus were used as Fluroscence Resonance Energy Transfer (FRET) pair. The nanosensor, which was termed fluorescent indicator protein for sialic acid (FLIP-SA), was successfully transformed into, and expressed in Escherichia coli BL21 (DE3) cells. The expressed protein of the nanosensor was isolated and purified. The purified nanosensor protein was characterized to assess the affinity, specificity, and stability in the pH range. The developed nanosensor exhibited FRET change after addition to NeuAc. The developed nanosensor was highly specific, exhibited pH stability, and detected NeuAc levels in the nanomolar to milimolar range. FLIP-SA was successfully introduced in bacterial and yeast cells and reported the real-time intracellular levels of NeuAc non-invasively. The FLIP-SA is an excellent tool for the metabolic flux analysis of the NeuAc biosynthetic pathway and, thus, may help unravel the regulatory mechanism of the metabolic pathway of NeuAc. Furthermore, FLIP-SA can be used for the high-throughput screening of E. coli mutant libraries for varied NeuAc production levels.

Study on Methyl Esterification of Salicylic Acid Using an Intensified Fixed Bed Reactor

2019 ◽  
Vol 17 (8) ◽  
Author(s):  
Gaodong Yang ◽  
Si Chen ◽  
Xiabing Li ◽  
Chengzhi Liu ◽  
Jian He ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Exchange Resin ◽  
Fixed Bed ◽  
Cation Exchange Resin ◽  
Fixed Bed Reactor ◽  
Catalyst Loading ◽  
Optimal Conditions ◽  
Methyl Esterification ◽  
Acid Catalyzed ◽  
Good Agreement

Abstract Methyl esterification of salicylic acid catalyzed by strong acidic cation exchange resin NKC-9 was carried out on an intensified fixed bed reactor (IFBR) to investigate the effects of different parameters and the results showed that the optimal conditions were as follows: circulation speed is 1.5 L· h−1, catalyst loading is 20 %, initial mole ratio of salicylic acid and methanol is 1:6 and reaction temperature is 343.15 K. The thermodynamics for the methyl esterification of salicylic acid have been studied to obtain the equilibrium constant from the experimental data at different temperature. PH, E-R and LHHW models were used to correlate the kinetic data in the temperature range from 328.15 to 348.15 K. The calculated value is in good agreement with experimental value, indicating that all the models can be used to accurately describe the process of the methyl esterification of salicylic acid.

scholarly journals Natural Products from Scorzonera aristata (Asteraceae)

2010 ◽  
Vol 5 (5) ◽  
pp. 1934578X1000500 ◽  
Author(s):  
Manuela Jehle ◽  
Johanna Bano ◽  
Ernst P. Ellmerer ◽  
Christian Zidorn
Keyword(s):  
Natural Products ◽  
Methyl Ester ◽  
Chlorogenic Acid ◽  
Caffeic Acid ◽  
Acid Methyl Ester ◽  
Quinic Acid ◽  
The South ◽  
Caffeic Acid Derivatives ◽  
Aerial Parts ◽  
Acid Methyl

The aerial parts of Scorzonera aristata Ramond ex DC., collected in the South Tyrolean Dolomites, yielded the flavonoids quercetin 3- O-glucoside, rutin, and isoorientin, and the caffeic acid derivatives chlorogenic acid, 4,5-dicaffeoyl quinic acid, and 3,5-dicaffeoyl quinic acid. Sub-aerial parts contained caffeic acid methyl ester, 3,5-dicaffeoyl quinic acid, and the triterpenes 3α-hydroxyolean-5-ene, lupeol, and magnificol. Chemosystematic implications of the isolated compounds are discussed briefly.

scholarly journals Kinetic studies on the acid hydrolysis of the methyl ketoside of unsubstituted and O-acetylated N-acetylneuraminic acid

1973 ◽  
Vol 133 (4) ◽  
pp. 623-628 ◽  
Author(s):  
A. Neuberger ◽  
Wendy A. Ratcliffe
Keyword(s):  
Sialic Acid ◽  
Acid Hydrolysis ◽  
Model Compound ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Neuraminic Acid ◽  
Acetylneuraminic Acid ◽  
Rate Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of the model compound 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl-α-d-neuraminic acid and neuraminidase (Vibrio cholerae) closely resembled that of the O-acetylated sialic acid residues of rabbit Tamm–Horsfall glycoprotein. This confirmed that O-acetylation was responsible for the unusually slow rate of acid hydrolysis of O-acetylated sialic acid residues observed in rabbit Tamm–Horsfall glycoprotein and their resistance to hydrolysis by neuraminidase. The first-order rate constant of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid by 0.05m-H2SO4 was 56-fold greater than that of 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl -α-d-neuraminic acid. Kinetic studies have shown that in the pH range 1.00–3.30, the observed rate of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid can be attributed to acid-catalysed hydrolysis of the negatively charged CO2− form of the methyl ketoside.

Stereodivergent synthesis of 1,4-dicarbonyls by traceless charge–accelerated sulfonium rearrangement

Science ◽  
2018 ◽  
Vol 361 (6403) ◽  
pp. 664-667 ◽  
Author(s):  
Dainis Kaldre ◽  
Immo Klose ◽  
Nuno Maulide
Keyword(s):  
Natural Products ◽  
Double Bond ◽  
Carbonyl Group ◽  
Organic Synthesis ◽  
Relative Configuration ◽  
Chiral Induction ◽  
Tremendous Importance ◽  
Acid Catalyzed ◽  
Quaternary Stereocenters ◽  
Drug Scaffolds

The chemistry of the carbonyl group is essential to modern organic synthesis. The preparation of substituted, enantioenriched 1,3- or 1,5-dicarbonyls is well developed, as their disconnection naturally follows from the intrinsic polarity of the carbonyl group. By contrast, a general enantioselective access to quaternary stereocenters in acyclic 1,4-dicarbonyl systems remains an unresolved problem, despite the tremendous importance of 2,3-substituted 1,4-dicarbonyl motifs in natural products and drug scaffolds. Here we present a broad enantioselective and stereodivergent strategy to access acyclic, polysubstituted 1,4-dicarbonyls via acid-catalyzed [3,3]-sulfonium rearrangement starting from vinyl sulfoxides and ynamides. The stereochemistry at sulfur governs the absolute sense of chiral induction, whereas the double bond geometry dictates the relative configuration of the final products.

Isolation, biochemical and immunological characterisation of two sea urchin glycoproteins bearing sulphated poly(sialic acid) polysaccharides rich in N-glycolyl neuraminic acid

Biochimie ◽  
1996 ◽  
Vol 78 (3) ◽  
pp. 171-182 ◽  
Author(s):  
N.K. Karamanos ◽  
A. Manouras ◽  
S. Anagnostides ◽  
E. Makatsori ◽  
T. Tsegenidis ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Sea Urchin ◽  
Neuraminic Acid
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