Pranab Ghosh

Greener approach toward one pot route to pyrazine synthesis

Abstract A very simple, cost effective, and environmentally benign method has been reported for the preparation of pyrazine derivatives of pentacyclic triterpenoids. The versatility of the method is determined by synthesizing a large number of pyrazine derivatives of smaller molecules.

Synthesis and Characterization of Biodegradable Polymer – Used as a Pour Point Depressant for Lubricating Oil

Additives based on polymers of alkyl methacrylate used in lubricant composition improve the viscometric and rheological properties of the lubricant and provide fuel economy. They are also looked upon to provide additional performance characteristics such as improved low temperature fluidity, dispersancy and thickening. However, the recent demand for eco-friendly technology guided us to incorporate the sunflower chemistry into the acrylate skeleton through the process of copolymerization in anticipation of getting an ideal blend of performance as well as eco-friendly chemistry. The present investigation comprises the homo and copolymerization of sunflower oil with different mass fraction of methyl methcrylate (MMA), decyl acrylate (DA) and styrene, characterizations and their evaluations as a pour point depressant in base oils.

Triterpenoids from Psidium guajava with Biocidal Activity.

In continuation of our studies on the phytochemical investigation of medicinal plants available in the foothills of Darjeeling and Teri, we report herein the isolation of two triterpenoids betulinic acid and lupeol from the leaf extract of Psidium guajava and their potential antimicrobial and phytotoxic activities. All the structures of the isolated compounds were confirmed by spectral (IR, NMR) analysis and by comparison with the literature reports.

Evaluation of sunflower oil as a multifunctional lubricating oil additive

The function of additives is either to enhance an already-existing property of the base fluid or to add a new property. Viscosity index improvers, antifoaming agents, emulsifiers, demulsifiers, and pour point depressants are examples of different kinds of additives. Most of the present day additives are synthetic acrylate based. But with increasing environmental awareness, the research in the area towards the synthesis of multifunctional biodegradable lubricating oil additive is increasing day by day. Hence, in our present work chemistry of biodegradable multifunctional lubricating oil additive based on vegetable oil (sunflower oil) has been investigated. In the present work solvent-free synthesis of homopolymer of sunflower oil was performed by two different ways; microwave irradiation method and thermal method using benzoyl peroxide as initiator. Characterization of the polymers was done by spectral (NMR, IR), GPC and viscometric analysis and finally performance evaluation was tested by standard ASTM methods. Performance evaluation as pour point depressant, viscosity modifier or viscosity index improver and antiwear in different base oils (BO1, BO2) was carried out by standard ASTM methods. Shear stability and oil thickening property of the polymers have also been investigated and reported here. Thermal stability of the polymers was determined by thermogravimetric analysis. A comparison of their performances has also been reported. The additive prepared by microwave-assisted method showed better viscosity index and pour point values as compared to thermally prepared additive. Thus, polymerized sunflower oil may be used as a potential biodegradable lube oil additive and hence the microwave-assisted protocol may be considered as a cost-effective greener approach for synthesis of lube oil additive.

Synthesis of friedelan triterpenoid analogs with DNA topoisomerase IIα inhibitory activity and their molecular docking studies

Five highly oxygenated friedelan derivatives (3a, 3b, 4, 5a and 5b) were synthesized. The structures of these compounds were established on the basis of spectral (IR, 1D and 2D NMR, MS etc.) and chemical data. The molecules, including the parent compounds were screened for three-dimensional (3D) molecular docking on the crystal structure of topoisomerase IIα (1 bgw for topoisomerase IIα, PDB). Compounds 3a and 5a showed a dose dependent inhibition of catalytic activity of human topoisomerase IIα.

Synthesis of bioactive 28-hydroxy-3-oxolup-20(29)-en-30-al with antileukemic activity.

An easy and efficient route to partial synthesis of bioactive 28-hydroxy-3-oxolup-20(29)-en-30-al (1), starting from betulinic acid (2), has been developed (eight steps, 44% overall yield). Structures of all the compounds were determined by spectral studies (IR, 1H, 13C NMR, MS, NOESY, COSY, etc.). Compound 1 and the precursors (2, 3, 5, and 7) showed antiproliferative activities against human K562 leukemia, murine WEHI3 leukemia, and murine MEL erythroid progenitor.

Studies on the additive performance of liquid crystal blended polyacrylate in lubricating oil

Homopolymer of decyl acrylate (D) was synthesised, characterised (Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR)) and evaluated for its additive performance as antiwear (AW), pour point depressant (PPD) and viscosity modifier (VM). Physical blends of the polymer were also made with three different types of liquid crystals (each containing three samples), evaluated and the results were compared. The study indicated that additive performances (AW, VM and PPD) of the blended composites were much better in comparison to the homopolymer of polydecyl acrylates.

Recent Approaches Toward Solid Phase Synthesis of β-Lactams

Since the discovery of penicillin in 1929, β-lactam antibiotics have been recognized as potentially chemotherapeutic drugs of incomparable effectiveness, conjugating a broad spectrum of activity with very low toxicity. The primary motif azetidin-2-one ring (β-lactam) has been considered as specific pharmacophores and scaffolds. With the advent of combinatorial chemistry and automated parallel synthesis coupled with ample interests from the pharmaceutical industries, recent trends have been driven mostly by adopting solid phase techniques and polymer-supported synthesis of β-lactams. The present survey will present an overview of the developments on the polymer-supported and solid phase techniques for the preparation of β-lactam ring or β-lactam containing antibiotics published over the last decade. Both unsubstituted and substitutions with different functional groups at various positions of β-lactams have been synthesized using solid phase technology. However, Wang resin and application of Staudinger [2+2] cycloaddition reaction have remained hitherto the major choice. It may be expected that other solid phase approaches involving different resins would be developed in the coming years.

Sodium dodecyl sulfate in water: greener approach for the synthesis of quinoxaline derivatives

Abstract A mild and efficient synthetic method has been developed for the preparation of biologically important quinoxalines in excellent yield from relatively safe precursor α-bromoketones and 1,2-diamines using catalytic amount of micellar sodium dodecyl sulfate in water at ambient temperature. The method is also found effective for the introduction of quinoxaline moiety into the ring A of pentacyclic triterpenoid, friedelin. Ambient reaction conditions, renewable catalytic condition, inherently safer chemistry, excellent product yields, and water as a reaction medium display both economic and environmental advantages.

Synthesis and Performance Evaluation of Vinyl Acetate-Maleic Anhydride Based Polymeric Additives for Lubricating Oil

Copolymer of vinyl acetate with maleic anhydride was synthesised and the prepared copolymer was esterified with different long chain alcohols (octyl, decyl, and dodecyl alcohol). The performance of the polymeric additives in different base oils was evaluated as viscosity modifier (VM), also called viscosity index improver and pour point depressant by standard ASTM methods. Intrinsic viscosity and viscometric molecular weight of the polymers were determined by Huggins and Mark-Houwink equation, respectively. It was found that the efficiency of the polymers as a VM increases with increasing the alkyl chain length of the used alcohol. Whereas, the efficiency as a pour point depressant increases with decreasing alkyl chain length of the used alcohol of the polymers.