Application of Deep Eutectic Solvents in the Synthesis of Substituted 2-Mercaptoquinazolin-4(3H)-Ones: A Comparison of Selected Green Chemistry Methods

In this study, deep eutectic solvents (DESs) were used as green and eco-friendly media for the synthesis of substituted 2-mercaptoquinazolin-4(3H)-ones from different anthranilic acids and aliphatic or aromatic isothiocyanates. A model reaction on anthranilic acid and phenyl isothiocyanate was performed in 20 choline chloride-based DESs at 80 °C to find the best solvent. Based on the product yield, choline chloride:urea (1:2) DES was found to be the most effective, while DESs acted both as solvents and catalysts. Desired compounds were prepared with moderate to good yields using stirring, microwave-assisted, and ultrasound-assisted synthesis. Significantly, higher yields were obtained with mixing and ultrasonication (16–76%), while microwave-induced synthesis showed lower effectiveness (13–49%). The specific contribution of this research is the use of DESs in combination with the above-mentioned green techniques for the synthesis of a wide range of derivatives. The structures of the synthesized compounds were confirmed by ¹H and ¹³C NMR spectroscopy.     

Oxidative 10-membered ring expansion and contraction of stereoisomeric 1(10)-unsaturated and 1,10-epoxy-5-oxo-5,10-secosteroids induced by peracids

The present study is concerned with the oxidative behaviour of unsaturated and epoxy 5-oxo-5,10-secosteroids in the presence of m-CPBA or TFAA-UHP as oxidants in order to investigate potential parameters controlling the chemoselectivity and regioselectivity. In the study we discovered a striking difference in the chemical behaviour of stereoisomeric compounds, (Z)- and (E)-3β-acetoxy-5,10-secocholest-1(10)-en-5-ones, as well as 1S,10R- and 1R,10R-epoxides. The secoketones were oxidized with exclusively C-6 migration and Baeyer–Villiger rearrangement product formation, whereas their stereoisomers provided the ring-contracted products, without lactone formation. The preferred conformation of expanded and contracted rings was established by NOESY correlations. The structures of two obtained lactones were also confirmed by X-ray analysis. The mechanistic and stereochemical aspects of these transformations are discussed.     

A Comparative Study of Enzymatically and Photochemically Polymerized Artificial Lignin Supramolecular Structures Using Environmental Scanning Electron Microscopy

Environmental scanning electron microscopy images of the self-assembled structures of enzymatically (DHP) and photochemically polymerized (PCP) artificial lignin are herein presented. Differences in the structural organization between DHP and PCP polymer at the supramolecular level were reported. Based on topological information, we proposed a hypothesis about possible new physiological roles of lignin in live plant cells and the ecological significance of possible in-vivo photochemical lignin polymerization. Copyright 2000 Academic Press.     

ATPases as Multi-Response Sensing System for Various Organic and Inorganic Analytes

Summary. The possibility of using synaptic plasma membrane (SPM) enzymes Na⁺/K⁺-ATPase and Mg²⁺-ATPase, isolated from rat brain, as a biological component of multi-response sensing system for detection of different compounds (alkaline and heavy metal salts, organic compounds) was studied. The method is based on the spectrophotometric determination of inorganic ortho-phosphate (P_i) that serves as a measure of the enzymatic activity in the presence of various analytes. The concentration of P_i, liberated by enzyme catalysed hydrolysis of adenosinetriphosphate (ATP), was followed spectrophotometrically, by single exposure to analytes or in the mixture. P_i was dose dependent on the analyte concentration. Alkaline elements (Na, K, Mg), heavy metals (Pb, Cd, Hg, Cu, Fe, Co, Zn), toxic organic compounds (pyridine, urea, chlorpyrifos), and some drugs (digoxin, gitoxin) showed diverse effects, inducing the inhibition or stimulation of the enzymes activity. Development of simple test method for simultaneous detection of the investigated analytes based on the variation of medium assay composition was discussed.     

Sums and Limits of Generalized Direct Families of Algebras

In this paper we introduce a generalization of direct families of algebras and we study their limits and sums. In the case of generalized direct families of algebras carried by idempotent algebras we investigate some subdirect decompositions of their sums. The results that we obtain generalize various results given by J.L. Chrislock and T. Tamura [2], M. iri and S. Bogdanovi [3-7], H. Mitsch [13], M. Petrich [14-16], B.M. Schein [23-24] and others.Supported by Grant 04M03B of RFNS through Math. Inst. SANU     

Mesomorphism of lanthanide-containing Schiff's base complexes with chloride counterions

Liquid crystalline complexes [Ln(LH) 3 Cl 3 ] have been synthesized, where Ln is a trivalent lanthanide ion (Pr-Lu, except Pm) and where LH is the Schiff's base ligand N -octadecyl4-tetradecyloxysalicylaldimine. Although the ligand does not exhibit mesomorphism, the complexes do (SmA phase). The mesophase behaviour of these compounds has been investigated by polarizing optical microscopy, differential scanning calorimetry and high temperature X-ray diffraction. The lanthanide complexes have much higher melting and clearing points than comparable complexes with nitrate or dodecyl sulphate counterions. In addition, the transition temperatures are virtually independent of the type of lanthanide ion. This behaviour is opposite to that observed for similar complexes with nitrate counterions [Ln(LH) 3 (NO 3 ) 3 ]. The differences in temperature dependence can be related to structural differences. Whereas in the nitrate complexes the Schiff's base ligand binds in a zwitterionic form, two-dimensional 1H NMR correlation spectroscopy (COSY) of [Lu(LH) 3 Cl 3 ] gives an indication that in the chloride complexes, besides coordination via the oxygen of molecules in the zwitterionic form, some of the Schiff's base ligands bind in a bidentate fashion (via the phenolic oxygen and the imine nitrogen).     

Assessment of Cardiorespiratory Interactions during Apneic Events in Sleep via Fuzzy Kernel Measures of Information Dynamics

Apnea and other breathing-related disorders have been linked to the development of hypertension or impairments of the cardiovascular, cognitive or metabolic systems. The combined assessment of multiple physiological signals acquired during sleep is of fundamental importance for providing additional insights about breathing disorder events and the associated impairments. In this work, we apply information-theoretic measures to describe the joint dynamics of cardiorespiratory physiological processes in a large group of patients reporting repeated episodes of hypopneas, apneas (central, obstructive, mixed) and respiratory effort related arousals (RERAs). We analyze the heart period as the target process and the airflow amplitude as the driver, computing the predictive information, the information storage, the information transfer, the internal information and the cross information, using a fuzzy kernel entropy estimator. The analyses were performed comparing the information measures among segments during, immediately before and after the respiratory event and with control segments. Results highlight a general tendency to decrease of predictive information and information storage of heart period, as well as of cross information and information transfer from respiration to heart period, during the breathing disordered events. The information-theoretic measures also vary according to the breathing disorder, and significant changes of information transfer can be detected during RERAs, suggesting that the latter could represent a risk factor for developing cardiovascular diseases. These findings reflect the impact of different sleep breathing disorders on respiratory sinus arrhythmia, suggesting overall higher complexity of the cardiac dynamics and weaker cardiorespiratory interactions which may have physiological and clinical relevance.     

Error estimates for some quadrature rules with maximal trigonometric degree of exactness

In this paper, we give error estimates for quadrature rules with maximal trigonometric degree of exactness with respect to an even weight function on ( ? π,π) for integrand analytic in a certain domain of complex plane. Copyright © 2013 John Wiley & Sons, Ltd.     

Model reduction and dynamic iteration for coupled nonlinear systems

The dynamical behavior of coupled systems is determined by different interconnected subsystems that are usually governed by entirely different physical laws and often act in different time and space scales. We discuss the simulation of coupled nonlinear systems using dynamic iteration combined with model order reduction. We also study the convergence of this approach and derive error estimates for approximate solutions. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)