A Simple Short Synthesis of Isotachin ‘C’

A short simple synthesis of Isotachin ‘C’ a sulphur containing aromatic ester isolated from New-Zealand Liver worts, Balantiopsis rosea has been described.     

Using polymeric hydroxypropyl methylcellulose as an alternative to ‘micellar catalysis’ to enable chemical reactions in water

Synthetic chemistry relies heavily on organic solvents which are often toxic and hazardous as well as expensive in purchase and disposal. The application of water as an alternative reaction medium is not only advantageous from an environmental and safety perspective but can also offer improved selectivity and reaction rates. The exploration of this new, sustainable approach comes along with an ever-growing spectrum of reaction procedures. In this current opinion, we provide an overview of a new methodology that uses a polymeric cellulose derivative, hydroxypropyl methylcellulose, to enable chemical reactions in water.     

Photoenzymatic Hydrogenation of Heteroaromatic Olefins Using ‘Ene’-Reductases with Photoredox Catalysts

Flavin-dependent ‘ene’-reductases (EREDs) are highly selective catalysts for the asymmetric reduction of activated alkenes. This function is, however, limited to enones, enoates, and nitroalkenes using the native hydride transfer mechanism. Here we demonstrate that EREDs can reduce vinyl pyridines when irradiated with visible light in the presence of a photoredox catalyst. Experimental evidence suggests the reaction proceeds via a radical mechanism where the vinyl pyridine is reduced to the corresponding neutral benzylic radical in solution. DFT calculations reveal this radical to be “dynamically stable”, suggesting it is sufficiently long-lived to diffuse into the enzyme active site for stereoselective hydrogen atom transfer. This reduction mechanism is distinct from the native one, highlighting the opportunity to expand the synthetic capabilities of existing enzyme platforms by exploiting new mechanistic models.     

Using amide conformation to ‘project’ the stereochemistry of an (−)-ephedrine-derived oxazolidine: a pair of pseudoenantiomeric chiral amido-phosphine ligands

Protection of a tertiary 2-formylbenzamide as an (−)-ephedrine-derived oxazolidine both forces the amide's stereogenic Ar–CO axis to adopt one of two possible diastereoisomeric conformations and protects the formyl group from attack during amide ortho-lithiation. By functionalising the amide in the 6-position, reactive sites (such as –CHO, –SR, –PR₂ groups) may be introduced which fall under the stereochemical influence, relayed by the amide, of the (−)-ephedrine-derived oxazolidine. This ‘projection’ of stereochemistry is exemplified by a pair of amido-phosphines, members of the first ever class of non-biaryl atropisomeric ligands, which are made functionally pseudoenantiomeric by the intervention of either one or two amide groups between the (−)-ephedrine-derived oxazolidine and the PPh₂ group. The pseudoenantiomeric amido-phosphines promote the palladium-catalysed asymmetric allylation of dimethyl malonate in 82 and −53% e.e., respectively.     

Prediction of an Organic Compound’s Biotransformation Time: A Study Using Avermectins

Moscow University Chemistry Bulletin - The current spread of the SARS-CoV-2 coronavirus is a challenge for the entire world. Ivermectin is a promising agent, which could be used to combat the...     

Symmetric binuclear complexes with an ‘end-off’ compartmental Schiff base ligand

Four binuclear transition metal(II) complexes: [Co₂L(-Cl)Cl₂] · 2H₂O, [Ni₂L(-Cl)Cl₂(H₂O)₂] · 2H₂O, [Cu₂L(-Cl)Cl₂] · 2H₂O and [Zn₂L(-Cl)Cl₂] · 2H₂O, where LH is the binucleating ligand 2,6-diformyl-4-methylphenol bis(2-hydrazino benzothiazole), were prepared. Based on the i.r. spectra, elemental analysis, conductivity measurements and thermal analysis, we propose that these complexes contain an endogenous phenoxide bridge and an exogenous chloride bridge. Magnetic and spectral data supports the existence of a weak antiferromagnetic interaction between the metal ions, and octahedral for Ni^II and a square pyramidal environment for remaining complexes. The compounds show significant growth inhibitory activity against the fungi, Aspergillus niger and Candida albicans, as compared to antibacterial activity against Bacillus cirroflagellosus and Pseudomonas auregenosa.     

SEM study of worn surface morphology of an indigenous ‘EPDM’ rubber

Ethylene Propylene Diene Monomer (EPDM) rubber emerges as a dominant elastomer for major engineering applications like automobiles, constructions, electric and electronic industries and many more. The major engineering properties of EPDM are its outstanding heat, ozone and weather resistance ability. The resistance to polar substances and steam is also good. EPDM rubber has a common use as seals in automobiles.In the present work friction and sliding wear behaviors of ethylene propylene diene monomer rubbers (EPDM) of different hardness have been studied against steel counterpart under dry working condition. Different hardness of EPDM have been achieved by adding different proportion (parts per hundred) of carbon black (CB) content with the main ingredients of EPDM. Tribo-testing has been carried out in a multi tribo-tester (Ducom, India). EPDM rubber of different hardness like 55 Å, 70 Å and 85 Å has been slid against EN-8 stainless steel roller of the tester. Experiments have been conducted with different rotational speeds of the wheel at a constant load of 25N for a constant duration of 900 s. The coefficient of friction (COF), mass loss and wear of EPDM rubbers have been determined from the test data. The worn surface morphology has also been studied using scanning electron microscope (SEM) and concluded accordingly.Present experimental work attempts to highlight some important tribo-characteristics of an indigenous EPDM rubber as well as to shed light on various possible areas of further research works.     

Report On ‘Water Chemistry: Using Field and Laboratory Experiences to Teach Scientific-Thinking Skills’

A new curriculum involving a blended general and organic chemistry course is being introduced at San Jose State University this fall by Stephen Branz and Maureen Scharberg. They shared their experiences in creating this new curriculum and described how they overcame resistance to this change from the university community to the workshop participants. The participants of the workshop then had the opportunity to examine the new curriculum and consider how they would approach problems in both the planning and implementation phase of such a project. The workshop participants created a final list of pros and cons for the planning stage (content, pedagogy, and transportability) and a list of possible strategies for the implementation stage (marketing, resources, and logistics).     

‘Lab-in-reaction-cell’ cyclic injection analysis as an opportunity for the miniaturization of flow analysis

The method of cyclic injection analysis in the ‘lab-in reaction-cell’ mode has been proposed for the miniaturization of flow analysis; the hydraulic scheme of this mode assumes the formation of the analytical forms of the analytes and their detection directly in the reaction cell of the cyclic injection analyzer through the combination of the latter with the measurement cuvette of a fiber optic spectrophotometer. The possibilities of the proposed solution are illustrated by the example of the determination of ‘active chlorine’ in aqueous media. A procedure has been developed for the automated photometric determination of ‘active chlorine’ in the range from 0.2 to 1.3 mg/L in aqueous media in a 125 μL sample, the duration of one analysis being 2.5 min.     

Green Biosynthesis of Silver Nanoparticles Using ‘Polygonum Hydropiper’ and Study its Catalytic Degradation of Methylene Blue

The green synthesis of silver nanoparticles with the small size and high stability paved the way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating biological risks in biomedical applications. Plant mediated synthesis of silver nanoparticles is gaining more importance owing its simplicity, rapid rate of synthesis of nanoparticles and eco-friendliness. In this study, focus on biosynthesis of silver nanoparticles using Polygonum hydropiper extract and its catalytic degradation of hazardous dye, methylene blue has been highlighted. The rapid reduction of silver (Ag) ions was monitored using UV-Visible spectrophotometer and showed formation of silver nanoparticles within less than one hour with maximum absorption of silver nanoparticles at 430 nm. The major functional groups present in the synthesis responsible for the formation of silver nanoparticles. It was identified by using Fourier Transform Infrared spectrophotometer (FTIR). Field Electron Scanning Microscope (FESEM) was used to characterise the nanoparticles synthesized using P.hydropiper. The morphology of silver nanoparticles was predominantly spherical and aggregated into irregular structure with average diameter of 60 nm. In addition, this report emphasizes the effect of the silver nanoparticles on the degradation rate of hazardous dyes by sodium borohydride (NaBH₄). The efficiency of silver nanoparticles as a promising candidate for the catalysis of organic dyes by NaBH₄ through the electron transfer process is established in the present study.     

Laser-scribed Graphene Electrodes as an Electrochemical Immunosensing Platform for Cancer Biomarker ‘eIF3d’

eIF3d is a protein biomarker which has a potential for the diagnosis of various cancers. Herein, a bio-platform was constructed for eIF3d sensing by using LSG and surface functionalization with anti eIF3d antibody via EDC/NHS chemistry. Following the surface modifications, XPS and several electrochemical methods were used. Difference in the signals were related to biomarker amounts between 75–500 ng/mL. LOD was calculated as 50.4 ng/mL. Selectivity of biosensor was tested by using of various interference molecules. EIF3d was also successfully detected in synthetic biological samples. Thus, to the best of our knowledge, this study is one of the rare studies on use of LSGs in immunosensor studies.     

‘A rendezvous with an old flame’: revisiting olefin hydrogenation with new rhodium and iridium catalysts

A novel tridentate hemilabile ligand 2 containing phosphine, imine and pyridyl donor groups has been prepared in analogy with the synthesis of the known related ligand 1. The reaction of 1 or 2 with 〚Rh(COE)₂Cl〛₂ resulted in the formation of the neutral complexes 〚Rh(L)Cl〛. By a method using 〚M(diene)Cl〛₂ as starting material, cationic complexes of the type 〚M(diene)(L)〛X were also obtained (M = Rh, diene = NBD, L = 1, 2; M = Ir, diene = COD, L = 1; X = BF₄, OTf). A comparative study of the catalytic activity of the new complexes towards the hydrogenation of various olefins has been reported. In particular, the catalysts of the type 〚Rh(L)Cl〛 are remarkably active when prepared in situ, especially for the reduction of hindered olefins.     

Atomic absorption determination of elements in solid samples using an electrothermal atomizer ‘crucible with separated zones’

A model of an electrothermal atomizer given the name ‘crucible with separated zones’ has been proposed. It provides the filtration of sample vapors through porous walls of a graphite tube placed in the atomization zone and heated independently of the evaporation zone. The inner volume of the tube is an isothermal analytical zone. The atomizer has been applied to the analysis of solid sea and river suspensions, DETATA concentrates of waters, and bottom sediments weighing 30–50 mg and more. As a result, the performance characteristics of the direct atomic absorption determination of Cd, Ag, and Pb in geochemical samples of complicated composition have been improved.     

A new class of indole alkaloid ‘elegansamine’ constructed from a monoterpenoid indole alkaloid and an iridoid

Elegansamine (1) isolated from Gelsemium elegans (Thailand) was proved to be a new type of alkaloid composed by the carbon-carbon linkage of a monoterpenoid indole alkaloid and a monoterpene unit having the iridoid skeleton.     

Efficient kinetic resolution of amino acids catalyzed by lipase AS ‘Amano’ via cleavage of an amide bond

Herein the efficient kinetic resolution of non-natural alpha-amino acids catalyzed by lipase AS ‘Amano’ via cleaving the amide bond is reported. The starting materials were the corresponding amino acid amides and the amino acids were generated with ees of up to 99% with E values of >600. These results indicated that the lipase AS ‘Amano’ could be a powerful amide hydrolase for the kinetic resolution of amino acid starting from the corresponding amino acid amides.