The synthesis of β-mannopyranosides by intramolecular aglycon delivery: scope and limitations of the existing methodology

1994 ◽  
Vol 72 (6) ◽  
pp. 1447-1465 ◽  
Author(s):  
Frank Barresi ◽  
Ole Hindsgaul
Keyword(s):  
Reaction Products ◽  
The Core ◽  
Naturally Occurring ◽  
Reaction Proceeds ◽  
Synthesis Approach

The synthesis of β-mannopyranosides by intramolecular aglycon delivery is shown to proceed with complete stereoselectivity in six separate cases. This strategy has been successfully applied to the synthesis of several disaccharides, including octyl 3,6-di-O-benzyl-4-O-(3,4,6-tri-O-benzyl-β-D-mannopyranosyl)-2-deoxy-2-phthalimido-β-D-glucopyranoside, a precursor of the naturally occurring β-D-Man-(1→4)-β-D-GlcNAc linkage, present in all N-linked glycoproteins. Exclusive formation of the β-mannosidic linkage has been confirmed in all six cases, since independently synthesized α-linked mannopyranoside standards were shown to be absent from the reaction products. The intramolecular stereocontrolled reaction proceeds even in the presence of competing methanol. The extension of this strategy to the synthesis of the core pentasaccharide of N-linked glycoproteins has revealed limitations to the methodology, especially when a block synthesis approach is investigated.

Solvent-free and efficient synthesis of bicyclic 2-pyridone derivatives for endoplasmic reticulum imaging

2021 ◽  
Author(s):  
Xiaoyun Ran ◽  
Qian Zhou ◽  
Jin Zhang ◽  
Shanqiang Wang ◽  
Gui Wang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Citric Acid ◽  
Core Structure ◽  
Solvent Free ◽  
Efficient Synthesis ◽  
The Core ◽  
Catalyst Free ◽  
Synthesis Approach ◽  
Ethylenediamine Derivatives

Started from citric acid (CA) and ethylenediamine derivatives, a solvent-free, catalyst-free and highly yield synthesis approach for bicyclic 2-pyridones was presented. Continuing to modify the core structure, a series of...

A Psychometric Approach to Heritage Language Studies

2013 ◽  
Vol 10 (2) ◽  
pp. 203-210
Author(s):  
Irina Sekerina
Keyword(s):  
Cognitive Abilities ◽  
Heritage Language ◽  
Critical Factor ◽  
Standardized Assessment ◽  
Dominant Language ◽  
The Core ◽  
Naturally Occurring ◽  
Language Studies ◽  
Ultimate Attainment ◽  
Effect Of Age

The central goal of the heritage language (HL) curriculum is to facilitate ultimate attainment of the language by advanced speakers. However, the field of HL studies faces a problem in how to accurately and efficiently identify and measure weaknesses and strengths of advanced HL speakers on their way to ultimate attainment. So far, only the age of arrival to the country where the dominant language is spoken has been formally investigated as the most critical factor that influences full professional proficiency and ultimate attainment of the HL. The field of HL studies needs to embrace a formal psychometric approach that will allow us to go beyond the effect of age of arrival to uncover contributions of other naturally occurring factors, i.e., genetic, physiological, cognitive, developmental and environmental. At the core of this approach lies a comprehensive standardized assessment of (a) proficiency in HL and (b) general cognitive abilities.

scholarly journals Influences on hepatitis B virus replication by a naturally occurring mutation in the core gene

Virology ◽  
2007 ◽  
Vol 365 (2) ◽  
pp. 285-291 ◽  
Author(s):  
Masaya Sugiyama ◽  
Yasuhito Tanaka ◽  
Fuat Kurbanov ◽  
Nobuaki Nakayama ◽  
Satoshi Mochida ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Virus Replication ◽  
Core Gene ◽  
The Core ◽  
Naturally Occurring ◽  
B Virus

Acid Stimulation Used in In-Situ Leaching Uranium

2010 ◽  
Author(s):  
Wen-sheng Liao ◽  
Li-min Wang ◽  
Yi-xuan Yao ◽  
Guo-ping Jiang ◽  
Hai-jun Zhao ◽  
...  
Keyword(s):  
Formic Acid ◽  
Injection Rate ◽  
Low Permeability ◽  
Reaction Products ◽  
Treatment Results ◽  
The Core ◽  
Fluid Systems ◽  
Core Permeability ◽  
Significant Production

Acidization was studied on a uranium sandstone deposit in Inner Mongolia with low–permeability and heavy calcium cementation. Acid dissolving test indicates that hydrochloric acid, formic acid and mud acid can easily dissolve formation minerals. With proper volumes and concentrations of acids used, the risk of precipitation of reaction products could be minimized. Core flow acidizing trial shows that the acidic fluid systems of hydrochloride acid, formic acid or acetic acid can significantly improve the core permeability. The average permeability has increased by 763 percent for the above three systems. But mud acid didn’t increase the core permeability; on the contrary, it caused formation damage, and led to lowering permeability. In the pilot test, the injection rate has improved by 118 percent for 6 wells. The acid treatment results indicate that a significant production enhancement of wellfields can be achieved by acid stimulation.

WD+AGB star systems as the progenitors of type Ia supernovae

2018 ◽  
Vol 14 (S343) ◽  
pp. 540-541
Author(s):  
Bo Wang
Keyword(s):  
Type Ia Supernovae ◽  
Population Synthesis ◽  
Final Phase ◽  
Common Envelope ◽  
The Core ◽  
Delay Times ◽  
Careful Treatment ◽  
Type Ia ◽  
Ia Supernovae ◽  
Synthesis Approach

AbstractWD+AGB star systems have been suggested as an alternative way for producing type Ia supernovae (SNe Ia), known as the core-degenerate (CD) scenario. In the CD scenario, SNe Ia are produced at the final phase during the evolution of common-envelope through a merger between a carbon-oxygen (CO) WD and the CO core of an AGB secondary. However, the rates of SNe Ia from this scenario are still uncertain. In this work, I carried out a detailed investigation on the CD scenario based on a binary population synthesis approach. I found that the Galactic rates of SNe Ia from this scenario are not more than 20% of total SNe Ia due to more careful treatment of mass transfer, and that their delay times are in the range of ∼90 − 2500 Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times.

scholarly journals Efficient Total Synthesis of Lissodendrin B, 2-Aminoimidazole Marine Alkaloids Isolated from Lissodendoryx (Acanthodoryx) fibrosa

Marine Drugs ◽  
2019 ◽  
Vol 18 (1) ◽  
pp. 36
Author(s):  
Xianfeng Wei ◽  
Xuelong Hu ◽  
Rilei Yu ◽  
Shengbiao Wan ◽  
Tao Jiang
Keyword(s):  
Total Synthesis ◽  
Triple Bond ◽  
Coupling Reactions ◽  
Sonogashira Coupling ◽  
Marine Alkaloids ◽  
Reaction Conditions ◽  
The Core ◽  
Analog Synthesis ◽  
Biological Studies ◽  
Synthesis Approach

Lissodendrin B is a 2-aminoimidazole alkaloid bearing a (p-hydroxyphenyl) glyoxal moiety that was isolated from the Indonesian sponge Lissodendoryx (Acanthodoryx) fibrosa. We reported the first efficient total synthesis of Lissodendrin B. The precursor 4,5-disubstituted imidazole was obtained through Suzuki coupling and Sonogashira coupling reactions from 4-iodoimidazole. C2-azidation and reduction of the azide then provided the core structures of Lissodendrin B. Subsequent triple-bond oxidation, demethylation, and deacetylation gave the final product. The synthesis approach consists of ten steps with an overall yield of 1.1% under mild reaction conditions, and it can be applied for future analog synthesis and biological studies.

Stereoselective Synthesis of the Core of Naturally Occurring Anti-HIV Isolitseane B

2007 ◽  
Vol 4 (4) ◽  
pp. 232-233 ◽  
Author(s):  
Paul Bremond ◽  
Elodie Girardeau ◽  
Yoann Coquerel ◽  
Jean Rodriguez
Keyword(s):  
Stereoselective Synthesis ◽  
The Core ◽  
Naturally Occurring ◽  
Anti Hiv

Experimental Analysis of CO2 Injection on Permeability of Vuggy Carbonate Aquifers

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Ibrahim M. Mohamed ◽  
Jia He ◽  
Hisham A. Nasr-El-Din
Keyword(s):  
Flow Rate ◽  
Initial Permeability ◽  
Co2 Injection ◽  
Reaction Products ◽  
The Core ◽  
Injection Flow Rate ◽  
Injection Flow ◽  
Injection Scheme ◽  
Core Permeability ◽  
Permeability Alteration

Reactions of CO2 with formation rock may lead to an enhancement in the permeability due to rock dissolution, or damage (reduction in the core permeability) because of the precipitation of reaction products. The reaction is affected by aquifer conditions (pressure, temperature, initial porosity, and permeability), and the injection scheme (injection flow rate, CO2:brine volumetric ratio, and the injection time). The effects of temperature, injection flow rate, and injection scheme on the permeability alteration due to CO2 injection into heterogeneous dolomite rock is addressed experimentally in this paper. Twenty coreflood tests were conducted using Silurian dolomite cores. Thirty pore volumes of CO2 and brine were injected in water alternating gas (WAG) scheme under supercritical conditions at temperatures ranging from 21 to 121 °C, and injection rates of 2.0–5.0 cm3/min. Concentrations of Ca++, Mg++, and Na+ were measured in the core effluent samples. Permeability alteration was evaluated by measuring the permeability of the cores before and after the experiment. Two sources of damage in permeability were noted in this study: (1) due to precipitation of calcium carbonate, and (2) due to migration of clay minerals present in the core. Temperature and injection scheme don't have a clear impact on the core permeability. A good correlation between the initial and final core permeability was noted, and the ratio of final permeability to the initial permeability is lower for low permeability cores.

Naturally occurring hepatitis B virus mutants with deletions in the core promoter region

1994 ◽  
Vol 20 (6) ◽  
pp. 837-841 ◽  
Author(s):  
Tomasz Laskus ◽  
Jorge Rakela ◽  
Myron J. Tong ◽  
Marek J. Nowicki ◽  
James W. Mosley ◽  
...  
Keyword(s):  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Promoter Region ◽  
Core Promoter ◽  
Core Promoter Region ◽  
The Core ◽  
Naturally Occurring ◽  
B Virus
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