ChemInform Abstract: OCTAFLUOROTOLUENE AS A REAGENT FOR THE SELECTIVE PROTECTION OF ALCOHOLIC AND PHENOLIC FUNCTIONS. SYNTHESIS AND CLEAVAGE OF PERFLUOROTOLYL AND OTHER PERFLUOROARYL ETHERS OF STEROIDS AND OTHER MODEL COMPOUNDS

<div>Here, we newly propose the structure of protoaculeine B, an N-terminal moiety of the marine peptide toxin aculeine B, as possessing the cis-disubstituted tetrahydro-beta-carboline framework. We prepared two truncated model compounds that lack long-chain polyamine by one-step Pictet-Spengler reaction of tryptophan, and compared the NMR and mass spectra and chemical reactivity with those of natural protoaculeine B. The synthetic models reproduced the profiles of the natural product well, which was conclusive for the structural revision.</div>

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Nuances in Alzheimer’s Genetic Risk Reveal Differential Predictions of Non-demented Memory Aging Trajectories: Selective Patterns by APOE Genotype and Sex

Current Alzheimer Research ◽

10.2174/1567205016666190315094452 ◽

2019 ◽

Vol 16 (4) ◽

pp. 302-315 ◽

Cited By ~ 1

Author(s):

G. Peggy McFall ◽

Lars Bäckman ◽

Roger A. Dixon

Keyword(s):

Genetic Risk ◽

Growth Models ◽

Memory Performance ◽

Apoe Genotype ◽

Cognitively Impaired ◽

Latent Growth ◽

Latent Growth Models ◽

Selective Protection ◽

Underlying Mechanisms ◽

Apoe Genotypes

Background: Apolipoprotein E (APOE) is a prominent genetic risk factor for Alzheimer’s disease (AD) and a frequent target for associations with non-demented and cognitively impaired aging. APOE offers a unique opportunity to evaluate two dichotomous comparisons and selected gradations of APOE risk. Some evidence suggests that APOE effects may differ by sex and emerge especially in interaction with other AD-related biomarkers (e.g., vascular health). Methods: Longitudinal trajectories of non-demented adults (n = 632, 67% female, Mage = 68.9) populated a 40-year band of aging. Focusing on memory performance and individualized memory trajectories, a sequence of latent growth models was tested for predictions of (moderation between) APOE and pulse pressure (PP) as stratified by sex. The analyses (1) established robust benchmark PP effects on memory trajectories, (2) compared predictions of alternative dichotomous groupings (ε4- vs ε4+, ε2- vs ε2+), and (3) examined precision-based predictions by disaggregated APOE genotypes. Results: Healthier (lower) PP was associated with better memory performance and less decline. Therefore, all subsequent analyses were conducted in the interactive context of PP effects and sex stratification. The ε4-based dichotomization produced no differential genetic predictions. The ε2-based analyses showed sex differences, including selective protection for ε2-positive females. Exploratory follow-up disaggregated APOE genotype analyses suggested selective ε2 protection effects for both homozygotic and heterozygotic females. Conclusion: Precision analyses of AD genetic risk will advance the understanding of underlying mechanisms and improve personalized implementation of interventions.

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Hafnium(IV) Chloride Catalyzes Highly Efficient Acetalization of Carbonyl Compounds

Current Organic Synthesis ◽

10.2174/1570179416666190715100505 ◽

2019 ◽

Vol 16 (6) ◽

pp. 913-920 ◽

Cited By ~ 1

Author(s):

Israel Bonilla-Landa ◽

Emizael López-Hernández ◽

Felipe Barrera-Méndez ◽

Nadia C. Salas ◽

José L. Olivares-Romero

Keyword(s):

Microwave Heating ◽

Reaction Times ◽

Protecting Groups ◽

Catalyst Loading ◽

Selective Protection ◽

Highly Efficient ◽

Aldehydes And Ketones ◽

High Yields ◽

Novel Catalyst ◽

Acid Labile

Background: Hafnium(IV) tetrachloride efficiently catalyzes the protection of a variety of aldehydes and ketones, including benzophenone, acetophenone, and cyclohexanone, to the corresponding dimethyl acetals and 1,3-dioxolanes, under microwave heating. Substrates possessing acid-labile protecting groups (TBDPS and Boc) chemoselectively generated the corresponding acetal/ketal in excellent yields. Aim and Objective: In this study. the selective protection of aldehydes and ketones using a Hafnium(IV) chloride, which is a novel catalyst, under microwave heating was observed. Hence, it is imperative to find suitable conditions to promote the protection reaction in high yields and short reaction times. This study was undertaken not only to find a novel catalyst but also to perform the reaction with substrates bearing acid-labile protecting groups, and study the more challenging ketones as benzophenone. Materials and Methods: Using a microwave synthesis reactor Monowave 400 of Anton Paar, the protection reaction was performed on a raging temperature of 100°C ±1, a pressure of 2.9 bar, and an electric power of 50 W. More than 40 substrates have been screened and protected, not only the aldehydes were protected in high yields but also the more challenging ketones such as benzophenone were protected. All the products were purified by simple flash column chromatography, using silica gel and hexanes/ethyl acetate (90:10) as eluents. Finally, the protected substrates were characterized by NMR 1H, 13C and APCI-HRMS-QTOF. Results: Preliminary screening allowed us to find that 5 mol % of the catalyst is enough to furnish the protected aldehyde or ketone in up to 99% yield. Also it was found that substrates with a variety of substitutions on the aromatic ring (aldehyde or ketone), that include electron-withdrawing and electrondonating group, can be protected using this methodology in high yields. The more challenging cyclic ketones were also protected in up to 86% yield. It was found that trimethyl orthoformate is a very good additive to obtain the protected acetophenone. Finally, the protection of aldehydes with sensitive functional groups was performed. Indeed, it was found that substrates bearing acid labile groups such as Boc and TBDPS, chemoselectively generated the corresponding acetal/ketal compound while keeping the protective groups intact in up to 73% yield. Conclusion: Hafnium(IV) chloride as a catalyst provides a simple, highly efficient, and general chemoselective methodology for the protection of a variety of structurally diverse aldehydes and ketones. The major advantages offered by this method are: high yields, low catalyst loading, air-stability, and non-toxicity.

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Lignin to Value-Added Chemical Synthesis

Current Analytical Chemistry ◽

10.2174/1573411016666200108152127 ◽

2020 ◽

Vol 16 ◽

Author(s):

Mahdieh Sharifi ◽

Ramyakrishna Pothu ◽

Rajender Boddula ◽

Inamuddin

Keyword(s):

Ionic Liquids ◽

Lignocellulosic Biomass ◽

Academic Research ◽

Power Saving ◽

Value Added ◽

Glycerol Ether ◽

Model Compounds ◽

Lignin Model Compounds ◽

Biomass Activity ◽

Lignin Model

Background: There is a developing demand for innovation in petroleum systems replacements. Towards this aim, lignocellulosic biomass suggested as a possible sustainable source for the manufacturing of fuels and produced chemicals. The aims of this paper are to investigate different kinds of β-O-4 lignin model compounds for the production of value-added chemicals in presence of ionic liquids. Especially, a cheap β-O-4 lignin model Guaiacol glycerol ether (GGE) (Guaifenesin) is introduced to produce valuable chemicals and novel products. Methods: Research related to chemical depolymerization of lignocellulosic biomass activity is reviewed, the notes from different methods such as thermal and microwave collected during at least 10 years. So, this collection provides a good source for academic research and it gives an efficient strategy for the manufacturing of novel value-added chemicals at an industrial scale. Results: This research presented that ionic liquid microwave-assisted is a power saving, cost efficient, fast reaction, and clean way with high selectively and purity for production of high value chemicals rather that conversional heating. Guaiacol and catechol are some of these valuable chemicals that is produced from β-O-4 lignin model compounds with high word demands that are capable to produce in industry scale. Conclusion: The β-O-4 lignin model compounds such as Guaiacol glycerol ether (GGE) (Guaifenesin) are good platform for developing food materials, perfumery, biorefinery, and pharmaceutical industry by ionic liquids-assisted lignin depolymerization method.

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Screening of novel ascomycetes for the production of laccase enzyme using different lignin model compounds

International Journal of Pharma and Bio Sciences ◽

10.22376/ijpbs.2016.7.4.b452-458 ◽

2016 ◽

Vol 7 (4) ◽

Author(s):

RAJESHRI PATEL J ◽

LAKSHMI BHASKARAN

Keyword(s):

Model Compounds ◽

Lignin Model Compounds ◽

Lignin Model ◽

Laccase Enzyme

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Study on the precision of the activated charcoal solvent desorption procedure - Correlation of desorption efficiencies

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19811332 ◽

1981 ◽

Vol 46 (6) ◽

pp. 1332-1347 ◽

Cited By ~ 2

Author(s):

Martin Koval

Keyword(s):

Activated Charcoal ◽

Carbon Disulphide ◽

Internal Standard ◽

Standard Addition ◽

Published Data ◽

Single Factor ◽

Gas Chromatograph ◽

Model Compounds ◽

Single Factor Analysis ◽

Acceptable Agreement

The described method uses activated charcoal sampling tubes for air sampling. Adsorbed compounds are eluted by the static desorption procedure with 1 ml of carbon disulphide, 0.5 ml of the supernatant is filtered off and, after internal standard addition, analysed on a gas chromatograph. Using synthetic calibration mixtures of model organic compounds with air, cumulative sampling and desorption efficiencies for 24 substances were determined for concentration ranges and sample volumes according to current Czechoslovak hygienic standards. Experimental results were treated with the single factor analysis of variance and the precision of the described procedure was estimated for the studied model compounds on the basis of residual sums of squares. Calculated values of cumulative sampling and desorption efficiencies and their precisions were compared with available published data and an acceptable agreement was found. In addition to that, cumulative sampling and desorption efficiencies were also found to be significantly correlated to molar volumes and other related molecular properties for some types of compounds.

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Configuration on the C=N double bond of monosubstituted amidines and amidoximes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19893245 ◽

1989 ◽

Vol 54 (12) ◽

pp. 3245-3252 ◽

Cited By ~ 13

Author(s):

Bernard Tinant ◽

Janine Dupont-Fenfau ◽

Jean-Paul Declercq ◽

Jaroslav Podlaha ◽

Otto Exner

Keyword(s):

Double Bond ◽

Nitrogen Atom ◽

Steric Effects ◽

Model Compounds ◽

X Ray ◽

Analogous Model

Configuration on the C=N double bond of amidines and amidoximes is controlled by steric effects on the second nitrogen atom but there is a difference in the case of N’-monosubstituted derivatives: amidines prefer E configuration (conformation around the C-N bond sp) and amidoximes Z configuration (conformation ap). This was confirmed by the X-ray structures of two analogous model compounds N,N’-dimethyl-4-nitrobenzamidine (monoclinic, P21c, a = 10.855(3), b = 11.043(3), c = 8.593(3) Å, β = 105.69(2)°, V = 991.8(5) Å3, Z = 4, Dx = 1.29 g cm-3, CuKα, λ = 1.5418 Å, μ = 7.91 cm-1, F(000) = 408, T = 291 K, R = 0.065 for 1 265 observed reflections) and N’-methyl-4-nitrobenzamidoxime (monoclinic, P21/a, a = 6.699(2), b = 24.178(9), c = 6.075(2) Å, β = 106.20(3)°, V = 944.9(6) Å3, Z = 4, Dx = 1.37 g cm-3, CuKα, λ = 1.5418 Å, μ =9.22 cm-1, F(000) = 408, T = 291 K, R = 0.079 for 1 278 observed reflections).

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