The use of the acetolysis reaction for the investigation of natural phospholipids

1. When the acetolysis reaction is used to study the molecular types of natural phospholipids or to determine the bound glycerol, the possibility of a distortion of the results of analysis through the formation of by-products must be taken into account. 2. In order to prevent the formation of aldehyde acylals, the phospholipids undergoing analysis must first be freed from plasmalogens.     

The acetolysis of 2-acetoxyalkyltellurium trihalides

The reaction of six 2-acetoxyalkyltellurium trihalides in refluxing dry acetic acid yields haloacetates in addition to the previously observed diacetates. The haloacetates are formed either through direct cleavage of the carbon–tellurium bond with retention of configuration or through initial formation of a neighboring group intermediate that is subsequently attacked by halide ion. Added lithium acetate leads to an increase in S_N2 attack on the tellurium carbon. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:85–93, 1998     

Theoretical investigation on enantioselective Biginelli reaction catalyzed by natural tartaric acid

In this study, enantioselective Biginelli reaction of aldehyde, β‐ketoester, and urea catalyzed by natural (2R, 3R)‐tartaric acid has been investigated using density functional theory calculations. The results indicate that the most favorable pathway involves a protonated imine from aldehyde and urea in the first step. Tartaric acid forms H‐bonds network with substrates enhancing the electrophilicity of protonated imine and the nucleophilicity of β‐ketoester. (R)‐3,4‐Dihydropyrimidin‐2‐(1H)‐ones is preferable for the reaction. The solvent effect is discussed in the prediction of enantiomeric excess (ee) values in ethanol and water. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Enzymatic hydrolysis reaction of phospholipids in monolayers

The hydrolysis reaction of , and , -dipalmitoylphosphatidylcholine (DPPC) catalized by bee venom phospholipase A₂ was studied in spreading monolayer at the water/air interface. DPPC and the hydrolysis products, palmitic acid and -lysophosphatidylcholine, palmitoyl were characterized at the interface by means of surface pressure, surface potential and ellipsometric measurements. Furthermore, mixed monolayers of reagents and products were investigated to ascertain their miscibility. The results show that the hydrolysis reaction can be followed by the decrease of surface pressure with time on subphases containing β-cyclodextrin, a well-known complexing agent of many amphiphilic compounds. The order of the reaction, the kinetic constant and other kinetic parameters are deduced.     

Substituent effect on the acetolysis of neophyl p-bromobenzenesulfonates

The substituent effect on the acetolysis of neophyl brosylates was analyzed successfully based on the analysis method of Yukawa-Tsuno. The basic concept of this method was strongly supported.     

The use of the reformatsky reaction for the synthesis of β-amino acids

The salts of α-bromo acids react gently with imines in tetrahydrofuran in the presence of zinc; after acid hydrolysis, β-amino acids are directly obtained.     

The use of glass capillary columns for the analysis of polar natural products

Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence.     

The use of amino acids in the mannich reaction

Amino acids have been found to participate as the amine component in the Mannich reaction with both ketones and phenols. The phenolic Mannich bases may be cyclized with sulfuric acid to 1,2-dihydro-4(3/H)isoquinolones. In the presence of thionyl chloride the same Mannich bases undergo lactonization to benz[f]-1,4-oxazepin-4(3H)ones.     

Comparative investigation of the fatty acid compositions of the phospholipids of marine invertebrates

The fatty acid (FA) compositions of the phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) of the muscle tissues of 13 species from seven types of marine invertebrates have been studied. In the PCs and PEs of all the animals the main FAs were the 20:53, 20:46, 16:0, 18:1, and 18:0 acids, although the representatives of each type had their own specific features in their FA composition. The main FAs in the PCs and PEs in the majority of animals investigated coincided, although there were exceptions. The most promising sources for the directed isolation of PCs or PEs enriched with certain FAs have been determined. The highest level of polyenic FAs and the highest unsaturation index were found in representatives of theCoelenterata andEchinodermata (stars) types. It was shown that the amount of polyenic acids as a fraction of the sum of the acyl and alkenyl radicals in the majority of animals investigated was greater in the PCs than in PEs.Institute of Marine Biology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Far Eastern State University, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 24–29, January–February, 1984.     

Theoretical investigation of the isomers photolysis reaction for chlorine nitrate

For the reactant ClONO₂ the equilibrium geometry and energy have been calculated by using various density functional (DFT) theory methods. The harmonic vibrational frequencies were computed using the B3LYP method for the ground state of the reactant; the results were in good agreement with those of the experiment. It was shown that the DFT methods were superior to other ab initio methods in optimizing geometry and predicting vibrational frequencies. In the process of forming the products from the dissociation reactions of ClONO₂, the results indicated it undergoes the TS₂, but not the TS₁ transition state. According to the relative energies of various species, the potential energy surface reflected intuitively the mechanisms of these dissociation reactions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 94: 44–50, 2003     

The Kulinkovich hydroxycyclopropanation reaction in natural product synthesis

The Kulinkovich cyclopropanation reaction provides a flexible and convenient method for the synthesis of cyclopropanols. Together with the diverse chemistry of the cyclopropanol unit, it offers access to a wide range of functionalised unsaturated and saturated compounds. The successful use in the synthesis of natural compounds is outlined in this perspective.     

The use of ESR spectroscopy for the investigation of dosimetric properties of egg shells

Electron spin resonance (ESR) spectroscopy was used to investigate the dosimetric properties of chicken egg shells. The ESR spectra of the irradiated egg shell were found to have an asymmetric absorption characterized by a major resonance at g=2.0019 and a minor resonance at g_||=1.9980. The study was carried out on g=2.0019 signal because of the accuracy of measurements and the possibility of using it as ESR dosimeter. The activation energy (E), frequency factor (k₀) and mean-life (τ) were calculated to be 1.50±0.10 eV, 2×10¹³ s⁻¹ and (4.4±0.4)×10⁴ year respectively. Dose–response was investigated between dose ranges of 1 Gy and 10 kGy for ⁶⁰Co γ-rays. Dose–response was found to be appropriate for dosimetry in the range 3 Gy to 10 kGy. The lower limit of observable doses for egg shell sample was about 3 Gy. The other ESR dosimetric parameters of egg shell samples, fading characteristic, light effect, dose-rate dependence and energy dependence, have also been studied in detail. Apart from its non-tissue equivalence, egg shell has very good dosimetric properties with insignificant fading, light independence, linearity in dose–response (3 Gy–10 kGy), dose-rate independence and independence from energy above 500 keV. It suggests that egg shell may be used as a retrospective γ radiation dosimetry after nuclear accidents or other short accidental radiation events.     

The use of emanation thermal analysis for the investigation of radioactive waste fixation processes

The process of incorporation of radioactive wastes into a suitable matrix to form a stable product for long term disposal has been studied. The changes, occuring during the thermal treatment with glassy materials, i.e. drying, transformation processes, sintering, melting, etc. have been followed using emanation (radon) thermal analysis. This method was found useful in solving the problems of process development.     

The investigation of spin-orbit effect for the F((2)P)+HD reaction

In this paper, we employ the time-dependent quantum wave packet method to study the reaction of F((2)P(3/2), (2)P(1/2)) with HD on the Alexander-Stark-Werner potential energy surface. The reaction probabilities and total integral cross sections of the spin-orbit ground and excited states for the two possible products of the system are calculated. Because the reaction channel of the excited spin-orbit state is closed at the resonance energy, the resonance feature does not appear in the reaction probabilities and cross section for the F((2)P(1/2))+HD(v=j=0)-->HF+D reaction, in contrast with that found for the ground spin--orbit state. We also compare the average cross sections of the two possible products with the experimental measurement. The resonance peak in the present average cross section for the HF+D product is slightly larger than the experimental result, but much smaller than that of the single-state calculations on the potential energy surface of Stark and Werner. It seems that the spin--orbit coupling would play a relatively important role in this reaction. Moreover, the isotope effects of the ground and excited spin--orbit states and the reactivity of the two product channels from the excited spin--orbit state are presented.     

Thermochemical investigation of natural antlerite

Thermal and thermochemical investigations of natural hydroxyl-bearing copper sulfate Cu₃SO₄(OH)₄??antlerite have been carried out. The stages of its thermal decomposition have been studied employing the Fourier-transform IR spectroscopy. The enthalpy of formation of antlerite from the elements ??_f H _m ^o (298.15?K)?=?(?1750?±?10)?kJ?mol^?1 has been determined by the method of oxide melt solution calorimetry. Using value of S _m ^o (298.15?K), equal to (263.46?±?0.47)?J?K^?1?mol^?1, obtained earlier by the method of adiabatic calorimetry, the Gibbs energy value of ??_f G _m ^o (298.15?K)?=?(?1467?±?10)?kJ?mol^?1 has been calculated.     

Mass-spectrometric investigation of natural coumarins

Summary The mass spectra of coumarin, umbelliferone, herniarin, and ostol have been studied.