Acetylation of lagochilin

The acetylation of lagochilin and its derivatives with acetic anhydride in the presence of pyridine has been studied by PMR spectroscopy. It has been shown that the manifestation of the polyfunctionality of lagochilin in acetylation reactions with acetic anhydride is connected with a change in the nature of the process of solvation of the reaction forms with the subsequent replacement of the hydrogen atoms of the hydroxy groups by acetyl groups.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 46–49, January–February, 1980.     

Synthesis of naphthyridines and phenanthrolines using catalysts based on transition and rare-earth metals

Liquid-phase condensation of 3-, 4-, and 8-aminoquinolines with aliphatic and aromatic aldehydes catalyzed by transition and rare-earth metal complexes is an efficient method for synthesis of substituted 1,7- and 1,6-naphthyridines and 1,10-phenanthrolines.Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 450054 Ufa; Eastern Scientific-Research Institute of Coal Chemistry, 620219 Sverdlovsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1139–1148, May, 1992.     

Nature of mechanically induced defects in polycrystalline hydrargillite and Al2O3-A1(OH)3 studied by radiation methods

Mechanical treatment of hydrargillite Al(OH)₃ in a vibrational grinder and in a ball-mill grinder increases the dispersion, the specific surface area, and the unit-cell constants. An x-ray amorphous phase forms. Differences in the nature and in the concentration of paramagnetic centers arise on irradiation (77 K) of the mechanically treated samples. Anion vacancies and oxygen ions with disrupted short-range order appear in the mechanically treated samples. Their concentration increases with increased time of mechanical treatment. Pulsed thermal treatment of hydrargillite forms the Al₂O₃-Al(OH)₃ system and anneals the mechanically induced defects.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1463–1467, July, 1990.     

Beiträge zur Chemie der Silicium-Stickstoff-Verbindungen. CV. Ringschlußreaktionen mit 1,5-Bis(alkylamino)trisildioxanen

1.5-Bis(methylamino)hexamethyltrisildioxane reacts in the presence of triethylamine easily with germanium tetrachloride (equ. 1) and ethyldichlorophosphine (equ.2) to give the formerly unknown inorganic eightmembered ring systems Si₃GeN₂O₂ and Si₃PN₂O₂. Respectively. By analogous reacting of silicon tetrachloride only open chained Cl₃Si? Nme? Sime₂? O? Sime₂? O? Sime? NHme (IV; equ. 3) is formed. With metallated 1.5-bis(alkylamino)trisildioxanes, dischlorodiorganylsilanes do not give the expected asymmetric-, but the symmetric cyclotetrasildioxdiazanes V–VII. Dichlorophenylborane, in an analogous reaction, leads to the novel eightmembered ring system BSi₃N₂O₂, but the exact position of the N and O atoms in the ring could not be fixed beyond any doubt. The novel sixmembered ring system BSi₂Ni₂O was realized in compound IX via equ. (6).     

Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques

We report on the enhanced demarcation between human atherosclerotic plaques and normal vessel wall obtained using time-resolved detection of laser-induced fluorescence rather than the customary time-integrated monitoring technique. A frequency-doubled mode-locked and cavity-dumped continuous wave dye laser was used for picosecond pulse generation at 320 nm, and photon-counting techniques were employed for the time-resolved signal monitoring from human aorta samples in vitro. Implications for imaging fluorescence angioscopy and spectroscopic guidance in laser ablation of plaque are indicated.     

High-speed liquid and thin-layer chromatography of polychlorinated biphenyls.

High-speed liquid chromatography in the system silica gel/dry n-hexane and ultraviolet spectrometry have been used to study the composition of various types of commercially available mixtures of chlorinated biphenyls. Special attention has been paid to the analysis of highly chlorinated products. In addition to data previously published, retention times are recorded for 11 individual polychlorinated biphenyls. The results of high-speed liquid chromatography are compared with those obtained in several normal and reversed-phase thin-layer chromatographic systems.     

Measurements of inelastic cross sections for the (j,m) = (2,0)→(3,0) rotational transition of CsF in collisions with atoms and molecules

Individual state-to-state rotational transitions have been resolved in small angle scattering of polarized CsF molecules on Ne, Ar, C₂, H₆, N₂, CO, CO₂, CHF₃ at center of mass energies of about 0.1 eV. The absolute inelastic cross sections range from 5Ų up to 600Ų.     

Solid state extrusion of thermoplastic elastomers 4

A solid state extrusion technique is applied as to produce oriented block copoly(ether ester) under various physical conditions. The morphology of the extruded samples is characterized in relation to the extrusion parameters and hard segment compositions of the polymer, using thermal analysis and X-ray methods. The lateral dimensions of the crystalline domains are found to be approximately 150 Å depending on the extrusion conditions. The statistics of the long range periodicity of the structure along the extrusion direction is in agreement with a one-dimensional two phase model, the crystalline portion of which does not vary much in thickness (35 – 45 Å). The unexpected increase in the long period and the thermal shrinkage suggest the existence of strained interlamellar amorphous chains (tie molecules). The observed variations in tensile properties are interpreted under the assumption that both the number of such tie molecules and their fully extended lengths are determined by the hard segment composition and the extrusion conditions. It is also argued that the increase in the glass transition temperature is not only a function of the composition of hard segments in the amorphous phase but also of the number of strained tie molecules.Herrn Dr. Dr. h. c. H. Hellmann zum 70. Geburtstag gewidmet.Part 3 cf. lit [11]     

Studies on amino acids and peptides-III. 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide,LR, as a new racemization free coupling reagent in peptide synthesis

The easily accessible 2,4-bis (4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, $\text{LR}$, has been reacted with salts of N-protected amino acids $\text{1}$ (Z-Gly-OH, Boc-Gly-OH, Boc-S-Ser(Bzl)-OH, Boc-S-Tyr(Bzl)-OH, Z-S-Arg(Z₂)-OH, and Z-S-Pro-OH), at room temperature in CH₂Cl₂ to give the intermediates $\text{2}$, mixed anhydrides. When $\text{2}$ is treated with two moles of a base and one mole of the salt of an amino acid ester $\text{3}$ (TosOH·H-Gly-OBzl, HCl·H-Gly-OBzl, HCl·H-Gly-OEt, and HCl·H-S-Phe-OtBu) at 0°C, the expected peptide $\text{4}$ is isolated in high yields. LR is also found to be a useful reagent in a fragment coupling between Z-Gly-S-Ala-OH and TosOH·H-S-Leu-OBzl). This tripeptide was tested by means of HPLC (deprotection and amino acid analysis according to Izumiya was not necessary), and no epimerization (<0.7 %) was observed.     

New method for the synthesis of 1,4-enynes by the cross-coupling of magnesium acetylides with allyl compounds

Conclusions A method was developed for the synthesis of 1,4-enynes by the cross-coupling of compounds of type (RCC)₂Mg and RCCMgBr with allyl alcohol derivatives using Ni(acac)₂-Ph₃P as the catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 907–908, April, 1984.