First stereoselective total synthesis of decytospolides A and B

The first synthesis of bioactive decytospolides A and B adopting an oxa-Michael addition as the key step is reported.     

Orientational order parameter studies on 3.Om and 3O.Om liquid crystals

Orientational order parameter S is evaluated in the nematic phase of six liquid crystal compounds, N-(p-n-propyl benzylidene)-p-n-alkoxy anilines, 3.Om and N-(p-n-propyloxy benzylidene)-p-n-alkoxy anilines, 3O.Om compounds with m = 6, 7 and 8, using different methods. The techniques employed are S from birefringence δn, Haller's approximation from (1?T/T_c) ^β, effective geometry parameter α_g and Vuks’ scaling factor S_C. The values of S obtained using the above methods are compared with one another and with the results on a number of liquid crystals; the liquid crystals favor isotropic Vuks’ method.     

Urea and thiourea derivatives of 3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1, 2, 4]triazolo[4,3-a]pyrazine: Synthesis,characterization, antimicrobial activity and docking studies

Abstract

An efficient and robust synthetic procedure was developed primarily for the synthesis of a precursor compound; 3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1, 2, 4]triazolo[4,3-a]pyrazine (11), from 2-chloropyrazine (7) through the chemical transformations such as hydrazine substitution, trifluoroacetyl group induction, cyclization and pyrazine ring reduction. A new series of urea derivatives 13a-e and thiourea derivatives 13f-j of compound 11 have been synthesized and the structures of all the compounds were confirmed using spectroscopic analyses such as IR, ¹H NMR, ¹³C NMR, LC-MS and HRMS. The newly synthesized compounds were screened for their in vitro antimicrobial activity against five bacteria and two fungi, in which compounds 13d, 13i and 13j displayed potential activity against bacterial strains and 13a, 13d, 13g and 13j against fungal strains with the MIC values in the range of 6.25–25.0 µg/mL. An overall comparison of the activity results revealed that thiourea derivatives contain better activity than that of urea compounds. Molecular docking studies on poly (ADP-ribose) polymerase 15 (ARTD7, BAL3) demonstrated that all the synthesized compounds possess significant binding energies (-8.1 to -9.8?kcal/mol) with no adverse effect in the active site of protein.     

Studies on Curcumin Loaded Poly(N-isopropylacrylamide) Silver Nanocomposite Hydrogels for Antibacterial and Drug Releasing Applications

Design of silver nanoparticles containing poly(N-isopropylarclamide) (PNIPAAm) hydrogels were prepared by free-radical polymerization of N-isopropylarclamide as an environmentally sensitive monomer and MBA as a crosslinker in an aqueous medium. The embedded silver nanocomposite hydrogels (AgNCH) structure were characterized by, UV-Vis, FTIR, DLS, TEM and X-ray analysis. Curcumin loading and release characteristics were performed for PNIPAAm hydrogel, silver ions loaded hydrogels as well as silver nanocomposite hydrogels. These curcumin loaded silver nanocomposite hydrogels exhibit excellent antibacterial action on Escherichia coli (E. coli). Therefore, the present study clearly provides novel antimicrobial hydrogels which are potentially useful in biomedical applications.     

Phase diagram study of CaBr2–CaHBr system

A study of binary, CaBr₂–CaHBr system was carried out by differential thermal analysis (DTA), covering the composition range from 100 % CaBr₂ to 100 % CaHBr between room temperature and 800 °C. From DTA results, the contour of solidus and liquidus temperatures with composition is plotted and the phase diagram of CaBr₂–CaHBr system is constructed. The system shows an eutectic reaction at 576 °C and the eutectic composition is 79.6 mol% CaBr₂. Co-existing phases in different phase fields are characterized by X-ray diffraction analysis.     

Preparation and Characterization of Some Substituted Benzyl N-Nitrosocarbamates Containing an N-2-(Methylthio)ethyl or a Bis(2-aminoethyl)sulfide Functionality

The synthesis and characterization of some substituted benzyl N-nitrosocarbamates with an N-2-(methylthio)ethyl or a bis(2-aminoethyl)sulfide functionality is reported, as a part of a long-term goal to design and prepare novel photolabile structures that could be used as substances for controlled release of alkylating and/or crosslinking agents. The synthesis was accomplished by reaction of benzyl chloroformates with the corresponding amines, resulting in the preparation of carbamates. The latter were subsequently nitrosated, utilizing two different N-nitrosation methods, to yield the target structures.     

ZnCl2+Urea,the deep eutectic solvent promoted synthesis of the spirooxindolopyrans and xanthenes through a pseudo-three-component approach

Various spirooxindolopyrans and xanthenes were synthesized efficiently through a pseudo-three-component reaction by using deep eutectic solvent (DES) ZnCl₂+Urea. The remarkable advantages of this reaction are the usage of an environmentally benign solvent (DES), simple purification method, operational simplicity, less reaction time, and higher yields making the reaction a green protocol.     

Synthesis of New Benzoxazaphosphinine/Benzoxazaphosphole/Diazaphosphaphenalene‐2‐sulfides using Lawesson's Reagent

Synthesis of new benzoxazaphosphinine/benzoxazaphosphole/diazaphosphaphenalene 2‐sulfides were accomplished by the reaction of Lawesson's reagent (LR) with 4‐bromo‐2‐[(phenylamino) methyl]phenol (1a), 4‐bromo‐2‐[(4‐chloro/bromo/methoxy/methylphenyl‐amino)methyl]phenol (1b–e), 4‐bromo‐2‐[(benzylamino)methyl]phenol (1f), 2‐amino‐4‐chlorophenol (2a)/2‐amino‐4‐methylphenol (2b), 1,8‐diaminonaphthalene (3) respectively in anhydrous toluene. Products 4a–f, 5a–b and 6 were characterized by IR, ¹H, ¹³C, ³¹P NMR and Mass spectra.