Ring expansion of cyclic ketones: The reliable determination of migration ratios for 3-keto steroids by 13C nuclear magnetic resonance and the general implications thereof

1979 ◽  
Vol 57 (13) ◽  
pp. 1557-1568 ◽  
Author(s):  
Vinod Dave ◽  
J. B. Stothers ◽  
E. W. Warnhoff
Keyword(s):  
Ring Expansion ◽  
Starting Material ◽  
Side Reactions ◽  
Reaction Products ◽  
Reliable Determination ◽  
13C Nuclear Magnetic Resonance ◽  
Single Exception ◽  
Diazoacetic Ester ◽  
First Time

Several ring-expansion reactions (diazomethane, diazoacetic ester, Tiffeneau–Demjanov, Baeyer–Villiger, and Schmidt) of 3-keto steroids have been reexamined to determine the true migration ratios for C-2 and C-4 in these unsymmetrical cyclohexanones. Migration ratios were measured to ±3% accuracy by integration of baseline-separated signals in the proton-decoupled 13Cmr spectra of total reaction products. This underexploited method provides for the first time a way to get accurate migration ratios without loss of components during separation and without interference from excess starting material under conditions minimizing side reactions. In contrast to numerous literature reports, all but one of the 16 reactions studied were found to give nearly the same amount of both possible A-homo products. (The single exception was the only reaction in which the A-homo product reacts markedly faster than the starting material.) This simple, consistent ∼1:1 pattern is that expected if migration is governed mainly by the electronic effect of the α- and α′-carbon atoms and not by any conformational or near-by-to-remote substituent effect.

Fast and reliable quantification of lignin reactivity via reaction with dimethylamine and formaldehyde (Mannich reaction)

Holzforschung ◽  
2017 ◽  
Vol 71 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Miao Wang ◽  
Elisabeth Sjöholm ◽  
Jiebing Li
Keyword(s):  
Mannich Reaction ◽  
Side Reaction ◽  
Side Reactions ◽  
Reaction Products ◽  
Reliable Determination ◽  
The Mannich Reaction ◽  
Reliable Quantification ◽  
Softwood Kraft Lignin ◽  
Nitrogen Contents

Abstract The influence of pH on the Mannich reaction (amino alkylation in the presence of formaldehyde) has been analyzed by liquid chromatography-mass spectrometry (LC-MS) with vanillin (VA) as a model compound and a purified softwood kraft lignin (SKL) as a substrate. The reaction products of VA were studied at pH 5, 7, and 9 at 60°C for 4 h. The Mannich adduct and side reaction products with methylene bridge were found at both pH 7 and 9, while only di-substituted by-products were observed at pH 5. Nitrogen contents determined from blank runs were substantial at pH 5 and negligible at pH 7. In VA or SKL, the resulting N-contents at pH 7 corresponded to a 76 or 62 mol% of the theory, respectively, i.e. based on the available C5 positions in phenolic guaiacyl units (G-units). In the case of SKL, 31P-NMR analysis confirmed a 77% conversion of all phenolic G-units into their C5 substituted derivatives. The Mannich reaction should be performed on lignin at pH 7 for 1 h to suppress unwanted side reactions, which could be observed by LC-MS under other pH conditions. The reaction is suitable for fast and reliable determination of reactive C5-positions in lignin by multiplication of the N-content of the reaction products with a factor of 1.6.

Endocranial Casts of Pre-Mammalian Therapsids Reveal an Unexpected Neurological Diversity at the Deep Evolutionary Root of Mammals

2017 ◽  
Vol 90 (4) ◽  
pp. 311-333 ◽  
Author(s):  
Julien Benoit ◽  
Vincent Fernandez ◽  
Paul R. Manger ◽  
Bruce S. Rubidge
Keyword(s):  
Brain Size ◽  
Accurate Determination ◽  
Mammalian Brain ◽  
Reliable Determination ◽  
Origin And Evolution ◽  
Show Evidence ◽  
Size And Morphology ◽  
First Time ◽  
Linear Manner

The origin and evolution of the mammalian brain has long been the focus of scientific enquiry. Conversely, little research has focused on the palaeoneurology of the stem group of Mammaliaformes, the Permian and Triassic non-mammaliaform Therapsida (NMT). This is because the majority of the NMT have a non-ossified braincase, making the study of their endocranial cast (sometimes called the “fossil brain”) problematic. Thus, descriptions of the morphology and size of NMT endocranial casts have been based largely on approximations rather than reliable determination. Accordingly, here we use micro-CT scans of the skulls of 1 Dinocephalia and 3 Biarmosuchia, which are NMT with a fully ossified braincase and thus a complete endocast. For the first time, our work enables the accurate determination of endocranial shape and size in NMT. This study suggests that NMT brain size falls in the upper range of the reptilian and amphibian variation. Brain size in the dicynodont Kawingasaurus is equivalent to that of early Mammaliaformes, whereas the Dinocephalia show evidence of a secondary reduction of brain size. In addition, unlike other NMT in which the endocast has a tubular shape and its parts are arranged in a linear manner, the biarmosuchian endocast is strongly flexed at the level of the midbrain, creating a near right angle between the fore- and hindbrain. These data highlight an unexpected diversity of endocranial size and morphology in NMT, features that are usually considered conservative in this group.

scholarly journals A new voltammetric platform for reliable determination of the sport performance-enhancing stimulant synephrine in dietary supplements using a boron-doped diamond electrode

2020 ◽  
Vol 12 (39) ◽  
pp. 4749-4758 ◽  
Author(s):  
M. Haššo ◽  
O. Sarakhman ◽  
D. M. Stanković ◽  
Ĺ. Švorc
Keyword(s):  
Sport Performance ◽  
Boron Doped Diamond ◽  
Reliable Determination ◽  
Diamond Electrode ◽  
Boron Doped ◽  
Boron Doped Diamond Electrode ◽  
Reliable Quantification ◽  
First Time ◽  
Performance Enhancing

For the first time, we propose a novel modification-free voltammetric platform for simple, fast and reliable quantification of the sport performance-enhancing stimulant synephrine on the screen-printed boron-doped diamond electrochemical sensor.

Empirical Interatomic Potential from Polarized and Depolarized Interaction-Induced Light Scattering Spectra for Gaseous Helium

2002 ◽  
Vol 216 (10) ◽  
Author(s):  
Mohamed Sayed Abdel El-Kader
Keyword(s):  
Light Scattering ◽  
Room Temperature ◽  
Interatomic Potential ◽  
Reliable Determination ◽  
Gaseous Helium ◽  
Interatomic Separation ◽  
Scattering Spectra ◽  
First Time ◽  
Potential Parameters

Polarized and depolarized interaction-induced light scattering spectra at room temperature (294.5±1) K have been used for deriving the empirical multiparameter Morse–Morse–Morse–spline–van der Waals interatomic potential. These new data of scattering are accurate enough to permit for the first time a reliable determination of the interatomic potential of the gaseous helium as a function of the interatomic separation. The potential parameters describing the location and depth of the attractive well are given by ε = 11.2±0.015 K,

A panel of mono- and dinucleotide microsatellite markers is required for reliable determination of the MSI status in colorectal cancer

2001 ◽  
Vol 120 (5) ◽  
pp. A599-A599
Author(s):  
C ARNOLD ◽  
A GOEL ◽  
J CARETHERS ◽  
L WASSERMAN ◽  
C COMPTON ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Microsatellite Markers ◽  
Reliable Determination

Colorimetric Determination of Fluoride in Drinking Groundwater using a Polymeric Zirconium Complex of 5-(2-Carboxyphenylazo)-8-Hydroxyquinoline

2013 ◽  
Vol 12 (7) ◽  
pp. 460-465
Author(s):  
Sameer Amereih ◽  
Zaher Barghouthi ◽  
Lamees Majjiad
Keyword(s):  
Drinking Water ◽  
Detection Limit ◽  
Complex Formation ◽  
Molar Absorptivity ◽  
Colorimetric Determination ◽  
Zirconium Complex ◽  
Reliable Determination ◽  
Percentage Recovery ◽  
Quantitation Limit

A sensitive colorimetric determination of fluoride in drinking water has been developed using a polymeric zirconium complex of 5-(2-Carboxyphenylazo)-8-Hydroxyquinoline as fluoride reagents. The method allowed a reliable determination of fluoride in range of (0.0-1.5) mg L-1. The molar absorptivity of the complex formation is 7695 ± 27 L mol-1 cm-1 at 460 nm. The sensitivity, detection limit, quantitation limit, and percentage recovery for 1.0 mg L-1 fluoride for the proposed method were found to be 0.353 ± 0.013 μg mL-1, 0.1 mg L-1, 0.3 mg L-1, and 101.7 ± 4.1, respectively.

Disability as a social phenomenon

2020 ◽  
pp. 22-38
Author(s):  
Natalia Guseva ◽  
Vitaliy Berdutin
Keyword(s):  
Social Protection ◽  
Russian Society ◽  
Stage Model ◽  
High Quality ◽  
Rehabilitation Programs ◽  
Current State ◽  
The Social ◽  
Consistent Solution ◽  
First Time

At present, the problem of establishing disability is a point at issue in Russia. Despite the fact that medical criteria for disability are being developed very actively, high-quality methods for assessing social hallmarks are still lacking. Since disability is a phenomenon inherent in any society, each state forms a social and economic policy for people with disabilities in accordance with its level of development, priorities and opportunities. We have proposed a three-stage model, which includes a system for the consistent solution of the main tasks aimed at studying the causes and consequences of the problems encountered today in the social protection of citizens with health problems. The article shows why the existing approaches to the determination of disability and rehabilitation programs do not correspond to the current state of Russian society and why a decrease in the rate of persons recognized as disabled for the first time does not indicate an improvement in the health of the population. The authors proposed a number of measures with a view to correcting the situation according to the results of the study.

Phytochemical Constituents of Annona reticulata and their Cytotoxic Activity

2020 ◽  
Vol 17 (3) ◽  
pp. 206-210
Author(s):  
Ty Viet Pham ◽  
Thang Quoc Le ◽  
Anh Tuan Le ◽  
Hung Quoc Vo ◽  
Duc Viet Ho
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Structural Determination ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
Phytochemical Constituents ◽  
First Time ◽  
Annona Reticulata

A phytochemical investigation of the leaves of Annona reticulata led to the isolation and structural determination of β-sitosterol (1), ent-pimara-8(14),15-dien-19-oic acid (2), ent-pimara- 8(14),15-dien-19-ol (3), quercetin (4), quercetin 3-O-α-L-arabinopyranoside (5), and a mixture of quercetin 3-O-β-D-galactopyranoside (6a) and quercetin 3-O-β-D-glucopyranoside (6b). Of these, compounds 2 and 3 were isolated from the genus Annona for the first time. Compound 3 showed strong cytotoxicity against SK-LU-1 and SW626 cell lines with IC50 values of 17.64 ± 1.07 and 19.79 ± 1.41 μg mL-1, respectively.

Development of an HPLC-UV Method for Quantification of Stattic

2019 ◽  
Vol 15 (6) ◽  
pp. 568-573
Author(s):  
Soheil Sedaghat ◽  
Ommoleila Molavi ◽  
Akram Faridi ◽  
Ali Shayanfar ◽  
Mohammad Reza Rashidi
Keyword(s):  
High Performance ◽  
Accurate Method ◽  
Plasma Samples ◽  
Promising Target ◽  
Relative Standard ◽  
Dimerization Inhibitor ◽  
Oncogenic Protein ◽  
First Time ◽  
Transcription 3

Background: Signal transducer and activator of transcription 3 (STAT3), an oncogenic protein found constitutively active in many types of human malignancies, is considered to be a promising target for cancer therapy. Objective: In this study for the first time, a simple and accurate method has been developed for the determination of a STAT3 dimerization inhibitor called stattic in aqueous and plasma samples. Methods: A reverse-phase high-performance liquid chromatography (RP-HPLC) composed of C18 column as stationary phase, and the mixture of acetonitrile (60%) and water (40%) as mobile phase with a UV detection at 215 nm were applied for quantification of stattic. The developed method was validated by Food and Drug Administration (FDA) guideline. Results: The method provided a linear range between 1-40 and 2.5-40 µg mL-1 for aqueous and plasma samples, respectively, with a correlation coefficient of 0.999. The accuracy (as recovery) of the developed method was found to be between 95-105% for aqueous medium and 85-115% for plasma samples. The precision (as relative standard deviation) for aqueous and plasma samples was less than 6% and 15%, respectively. The sensitivity of the developed method based on FDA guideline was 1 µg mL-1 for aqueous and 2.5 µg mL-1 for plasma samples. Conclusion: These results show that the established method is a fast and accurate quantification for stattic in aqueous and plasma samples.

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