Synthesis Properties and Characterization of Di Cyclopentadienyl Vanadium Bis Dialkyl and Alkylene Dithiophosphate Complexes

The reaction of dichloro bis cyclopentadienyl vanadium with O,O dialkyl and alkylene dithiophosphoric acids proceed in 1:2 molar ratio in refluxing benzene to yield di cyclopentadienyl vanadium bis O,O dialkyl and alkylene dithiophosphates, [Cp 2 V(S 2 P(OR) 2 ) 2 ], where R = Et, Pr i , Pr n , Bu i , Ph and [Cp 2 V (S 2 POGO) 2 ] where G = CMe 2 CMe 2 , CH 2 CEt 2 CH 2 , CH 2 CMe 2 CH 2 . These complexes are semi solids or solids soluble in common organic solvents. Elemental analysis, molecular weight determination, magnetic susceptibility, UV-vis spectrophotometer, IR, 1 H, 13 C, and 31 P NMR spectra indicate a hexa coordinated octahedral structure.     

Synthesis and Characterization of Chlorobis(cyclopentadienyl) Titanium(IV) and Zirconium(IV) O,O’-Dialkyl and Alkylene Dithiophosphates

Abstract

Reactions of O,O′-dialkyl and alkylene dithiophosphoric acids with bis (cyclopentadienyl) titanium(IV) and zirconium (IV) dichloride in a 1:1 molar ratio in refluxing benzene proceeds with elimination of HCl and formation of the substituted derivatives, Cp₂MCl[S₂P(OR)₂] (where R = Et, Pr-n, Pr-i, Bu-i and Ph), Cp₂MCl[S₂POGO] (where G = ?CH₂CMe₂CH₂?, ?CH₂CEt₂CH₂? and ?CMe₂CMe₂?), (M = Ti and Zr). The complexes are dark red and yellow solids, soluble in common organic solvents and monomeric in nature. These have been characterized on the basis of elemental analyses, molecular weight determinations, IR, and NMR (¹H, ¹³C, and ³¹P).

GRAPHICAL ABSTRACT      

Enantioselectivity Investigation of Short Polar Peptides with Different Positions in the Michael Reaction

This work reports the effectiveness of short polar peptides as asymmetric catalysts in Michael reactions to attain good yields of enantio- and diastereoselective isomers. In a comparison, glutamic acid and histidine produced greater ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric Michael addition reaction in water.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Development and Validation of a Method for Quantification of Favipiravir as COVID-19 Management in Spiked Human Plasma

In the current work, a simple, economical, accurate, and precise HPLC method with UV detection was developed to quantify Favipiravir (FVIR) in spiked human plasma using acyclovir (ACVR) as an internal standard in the COVID-19 pandemic time. Both FVIR and ACVR were well separated and resolved on the C18 column using the mobile phase blend of methanol:acetonitrile:20 mM phosphate buffer (pH 3.1) in an isocratic mode flow rate of 1 mL/min with a proportion of 30:10:60 %, v/v/v. The detector wavelength was set at 242 nm. Maximum recovery of FVIR and ACVR from plasma was obtained with dichloromethane (DCM) as extracting solvent. The calibration curve was found to be linear in the range of 3.1–60.0 µg/mL with regression coefficient (r²) = 0.9976. However, with acceptable r², the calibration data’s heteroscedasticity was observed, which was further reduced using weighted linear regression with weighting factor 1/x. Finally, the method was validated concerning sensitivity, accuracy (Inter and Intraday’s % RE and RSD were 0.28, 0.65 and 1.00, 0.12 respectively), precision, recovery (89.99%, 89.09%, and 90.81% for LQC, MQC, and HQC, respectively), stability (% RSD for 30-day were 3.04 and 1.71 for LQC and HQC, respectively at −20 °C), and carry-over US-FDA guidance for Bioanalytical Method Validation for researchers in the COVID-19 pandemic crisis. Furthermore, there was no significant difference for selectivity when evaluated at LLOQ concentration of 3 µg/mL of FVIR and relative to the blank.     

An improved method for the preparations of nanostructured lipid carriers containing heat-sensitive bioactives

Heat-sensitive bioactive compounds such as β-carotene and tocols, are widely used in the pharmaceutical and cosmetic fields. Their chemical stability in delivery systems is one of the major concerns in the production of nanostructured lipid carriers (NLCs). A previously established high-temperature high-pressure homogenisation technique involved in the preparation of NLCs can cause degradation of heat-sensitive compounds. Therefore, a novel preparation process needs to be developed to minimise the degradation of heat-sensitive active compounds during the preparation of NLCs. In this work, modified methods A and B were designed to minimise the degradation of β-carotene and tocols during the production of NLCs. These methods improved the chemical stability of heat-sensitive bioactive compounds (β-carotene and tocols) significantly compared to the previously established method. The physical stability of the formulation was maintained throughout study duration.     

Aqueous Electrochemistry of Anthraquinone and Its Correlation with the Dissolved States of a Cationic Surfactant

Cyclic voltammetry was employed to study the electrochemical behavior of anthraquinone (AQ) in aqueous solution at a glassy carbon electrode using the sodium salt of anthraquinone-2-sulphonic acid (AQS). The cyclic voltammograms show a reduction wave and a corresponding oxidation wave. The electrochemical reaction of AQ in aqueous solution involves a two electron transfer process followed by a coupled chemical reaction and exhibits strong pH dependence at low pH (<4). A satellite peak is also observed at the cathodic side of the reduction wave for the reduction of the sulfonate group of AQS. The electrochemical investigation was also carried out in the presence of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Similar redox behavior can be observed for the electrochemical reaction of AQS in the presence of CTAB solutions similar to the aqueous media. The electrochemical responses have been found to depend on the dissolved states of the surfactant. The current-potential behavior of AQS depends on the concentration of CTAB and micellization has a profound effect on the electrochemical behavior of AQ.     

Radioactivity in the Exclusive Economic Zone of east coast Peninsular Malaysia: distribution trends of <Superscript>137</Superscript>Cs in surface seawater

Large volumes of surface seawater samples were collected from thirty locations in the Exclusive Economic Zone (EEZ) of the east coast Peninsular Malaysia on June 2008 to study the activity concentrations of ¹³⁷Cs. The results will serve as additional information to the existing baseline data and is very useful for monitoring fresh input of anthropogenic radionuclide into Malaysian marine environment. In this study, the activity concentrations of ¹³⁷Cs were determined using co-precipitation technique, followed by Gamma Spectrometry measurement. The mean activity concentration of ¹³⁷Cs ranged between 3.40 and 5.89 Bq/m³. Higher activity concentrations were observed at the coastal and towards the south of Peninsular Malaysia and were aligned with the high turbidity. These may due to the rapid diffusion of ¹³⁷Cs from suspended particulates and fine sediments into surface seawater. The activity concentrations of ¹³⁷Cs observed in this study were slightly higher than the concentrations reported in seawater at the Straits of Malacca, Vietnam and Philippines. This might be because the study area received more input of ¹³⁷Cs that originated from global fallout and then deposited on land which later being transported subsequently into the coastal zone due to siltation and erosion processes. It could also be attributed to the intrusion of river waters containing higher concentrations of ¹³⁷Cs.     

New three-component condensation reaction: synthesis of 1-[(alkylthio)(phenyl)methyl]-naphthalene-2-ol catalyzed by bromodimethylsulfonium bromide (BDMS)

Bromodimethylsulfonium bromide acts as an efficient catalyst for one pot three component condensation reactions of aldehydes, 2-naphthol, and thiols in acetonitrile at room temperature. Various aliphatic and aromatic thiols undergo conjugate addition with in situ generated enone in acetonitrile and provide good yields. The main features of this procedure are mild reaction conditions, good yields, and operational simplicity.     

Electrochemical DNA biosensor for the detection of Trichoderma harzianum based on a gold electrode modified with a composite membrane made from an ionic liquid, ZnO nanoparticles and chitosan, and by using acridine orange as a redox indicator

An electrochemical DNA biosensor was developed that is based on a gold electrode modified with a nanocomposite membrane made from an ionic liquid, ZnO nanoparticles and chitosan. A single-stranded DNA probe was immobilized on this electrode. Acridine orange was used as the hybridization probe for monitoring the hybridization of the target DNA. The biosensor was capable of detecting target DNA in the concentration range from 1.0?×?10?C14 to 1.8?×?10?C4?mol?L-1, with a detection limit of 1.0?×?10?C15?mol?L-1. The approach towards constructing a DNA biosensor allows studies on the hybridization even with crude DNA fragments and also to analyze sample obtained from real samples. The results show that the DNA biosensor has the potential for sensitive detection of a specific sequence of the Trichoderma harzianum gene and provides a quick, sensitive and convenient method for the study of microorganisms.