Mappings of Finite Distortion:¶Discreteness and Openness

We establish a sharp integrability condition on the partial derivatives of a mapping with L ^p -integrable distortion for some p>n? 1 to guarantee discreteness and openness. We also show that a mapping with exponentially integrable distortion and integrable Jacobian determinant is either constant or both discrete and open. We give an example demonstrating the preciseness of our criterion.     

On the syntheses of 8-Heteroaryl-substituted 9-(β-D-Ribofuranosyl)-2,6-diaminopurines through Pd-catalyzed coupling in the presence of cupric oxide

Convenient methods for the preparation of 9-(β-D-ribofuranosyl) derivatives of 8-(2- and 3-thienyl)-2,6-diaminopurine and of 8-(2- and 3-furyl)-2,6-diaminopurine, which are potential antiviral agents has been worked out. The key step was a Pd(0)-catalyzed Stille coupling between 2- and 3-tributylstannylthiophene and 2- and 3-tributylstannylfuran and trimethylsilyl protected 9-(β-D-ribofuranosyl)-2,6-diamino-8-bro-mopurine. The use of N,N-dimethylformamide as solvent at 110° and dichloro(diphenylphosphine-propane)palladium(II) [PdC1₂(dppp)] with cupric oxide as co-reagent was essential in order to obtain a fast reaction and high yields.     

Quantum chemical calculations on the Peterson olefination with alpha-silyl ester enolates

The reaction of stabilized Peterson reagents (alpha-silyl ester enolates) with ketones has been studied theoretically and experimentally. Enolate geometry was studied by trapping experiments and NMR spectroscopy and was found to differ markedly with the nature of the base (LiHMDS vs LDA vs KHMDS). The chelating effect of the lithium counterion was found to be critical for the reaction. For the two ketones studied, the combined weight of experimental and computational data assigns geometrical selectivity to the initial addition transition state, though in general there appears to be a fine balance between three possible choices for the rate-determining step.     

Synthesis, Properties, and Reactions of 5-Substituted Derivatives of 2,3-Diphenylquinoxaline [1]

Catalytic hydrogenation of 5-nitro-2,3-diphenylquinoxaline led to the corresponding amine which, in turn, afforded products of nucleophilic substitution on reaction with alkoxymethylene derivatives. Thermal cyclization of selected alkoxymethylene derivatives yielded substituted pyridoquinoxalines. The conditions for successful hydrolysis of ester, decarboxylation of the acid, following chlorination of pyridone and reductive removal of the chlorine atom from it to produce parental heterocycle 2,3-diphenyl-pyrido[2,3-f]quinoxaline were found. All of the tested products of the nucleophilic substitution showed no antibacterial activity.     

Effects of short- and long-term ultraviolet B irradiation on the immune system of the common carp (Cyprinus carpio)

Carp (Cyprinus carpio) were repeatedly exposed to 0, 60, 120 and 240 mJ/cm2 ultraviolet B (UVB) radiation three times in 1 week (short-term exposure) or 12 times in 4 weeks (long-term exposure). The effect of UVB on the functioning of the carp immune system was studied on day 2 after the final irradiation. After short-term UVB exposure, the whole-blood respiratory burst and cytotoxic activity were markedly enhanced, with parallel responses in both the number of circulating granulocytes and in the plasma cortisol concentration of the fish. These changes were not detectable after long-term exposure. The respiratory burst by head kidney granulocytes was suppressed dose dependently after both exposures, but cytotoxic activity was not affected. Exposure to UVB also modulated lymphocyte functions: nonstimulated and PHA-stimulated proliferation of head kidney lymphocytes in vitro was enhanced by both short-term and long-term exposure. LPS-stimulated proliferation was not affected by exposure nor was the number of immunoglobulin-secreting cells in the head kidney. In long-term exposure, the highest dose reduced the level of plasma IgM. This study indicates that UVB irradiation induces immunomodulation in the blood and head kidney of the carp and that the effects of short- and long-term exposure differ from each other. The results emphasize the potentially harmful impact of increased solar UVB radiation on fish immune functions.     

Introduction of Amino Alcohols in the Ring-Opening Reaction of 3-bromo-2,5-dimethylthiophene 1,1-dioxide. A short diastereoselective synthesis of substituted ‘tetrahydrobenzo[a]pyrrolizidines’ (= octahydro-1H-pyrrolo[2,1-a]isoindoles) using L-prolinol

Tetrahydrobenzo[a]pyrrolizidines (= octahydro-1H-pyrrolo[2,1-a]isoindoles) and tetrahydrobenzo[a]indo-lizidines, (= decahydropyrido[2,1-a]isoindoles) were prepared stereoselectively in four steps through an amineinduced ring-opening of 3-bromo-2,5-dimethylthiophene 1,1-dioxide ( 1 ) with L -prolinol ( 9 ), piperidine-2-methanol ( 10 ), and piperidine-2-ethanol ( 11 ), yielding the dienes (2S)-1-[(2E,4Z)-4-bromohexa-2,4-dienyl]pyrrolidine-2-methanol ( 12 ), 1-[(2E,4Z)-4-bromohexa-2,4-dienyl]piperidine-2-methanol ( 13 ), and 1-[(2E,4Z)-4-bromo-hexa-2,4-dienyl]piperidine-2-ethanol ( 14 ; Scheme2), which, after conversion into their α,β-unsaturated esters, cyclized in a TiCl₄-catalyzed intramolecular Diets-Alder reaction (Scheme3). A discussion on the mechanism of the ring opening reaction including semiempirical and ab initio calculations is also presented.     

Pyridine-substituted hydroxythiophenes. IV. Preparation of 3- and 4-(2-, 3- and 4-pyridyl)-2-hydroxythiophenes

3-(2-, 3- and 4-Pyridyl)-2-methoxythiophenes have been prepared in good yields through the Pd(0)-cat-alyzed coupling of the three isomeric bromopyridines with 3-trimethylstannyl-2-methoxythiophene. This compound was prepared through halogen-metal exchange of 3-bromo-2-methoxythiophene followed by stannylation. 3-Bromo-2-methoxythiophene was prepared by dibromination and α-debromination of 2-methoxythiophen. Most attempts to demethylate 2-methoxy-3-pyridylthiophenes using a large variety of reagents failed, probably due to the instability and high reactivity of the desired 3-pyridyl-2-hydroxythiophene systems. Only 2-methoxy-3-(3-pyridyl)thiophene reacted with boron tribromide to give 3-(3-pyridyl)-3-thiolene-2-one, which only was stable in ether solution at ?20°. The attempted demethylation of 2-methoxy-3-(2-pyridyl)thiophene with trimethylsilane chloride/sodium iodide in refluxing acetonitrile led to a dimer. Demethylation of the 2-methoxy-3-pyridylthiophenes with dibenzyl diselenide and sodium borohydride gave 3-pyridylthiophan-2-ones. A number of other routes to prepare 3-pyridyl-2-hydroxythiophenes were also explored, but none of them gave the desired compounds. On the other hand, the 4-(2-, 3-, and 4-pyridyl)-2-hydroxythiophene systems could easily be prepared by hydrogen peroxide oxidation of the corresponding 4-pyridyl-2-thiopheneboronic esters, which were obtained from 2-bromo-4-pyridylthiophenes by halogen-metal exchange followed by reaction with ethyl borate. The 2-bromo-4-pyridylthiophenes were prepared by dibromination of the known 3-pyridylthiophenes to the 2,5-dibromo derivatives, and removal of the 2-bromine by halogen-metal exchange at ?100°, followed by hydrolysis. The ¹H nmr and ir spectroscopic investigations show that these quite stable 2-hydroxythiophene systems exist exclusively in the 4-pyridyl-3-thiolen-2-one forms.     

On the syntheses and some reactions of bis- and tris(methylthio)thiophenes

Reaction between various thienyllithium derivatives and dimethyl disulfide has been used for the preparation of 2,5-, 2,3-, and 3,4-bis(methylthio)thiophenes, as well as 2,3,4- and 2,3,5-tris(methylthio)thiophenes. Bromination of (methylthio)thiophenes with N-bromosuccinimide was found to be most convenient for the preparation of brominated (methylthio)thiophenes such as 3-bromo-2,5-bis(methylthio)- and 5-bromo-2,3-bis(methylthio)thiophene, 3,4-dibromo-2,5-bis(methylthio)-, 2,5-dibromo-3,4-bis(methylthio)- and 2,3-dibromo-4,5-bis(methylthio)thiophene as well as 3-bromo-2,4,5-tris(methylthio)thiophene. The reaction of methylthio substituted thienyllithium derivatives with methyl chloroformate was used for the syntheses of methyl methylthio substituted thiophenecarboxylates and using 1/3 of an equivalent for the direct preparation of methylthio substituted 3-thienylcarbinols as tris[2,4,5-tris(methylthio)-3-thienyl]carbinol.     

Hydrodynamic conditions for growth of large KDP crystals

Three-dimensional mass transfer is simulated. The factors determining the hydrodynamic conditions for efficient mass transfer in growth of large KDP single crystals (cross sections up to 45 × 45 cm²) from solutions in a real 300-l-crystallizer are established. The conditions for the motion of the supersaturated solution to the surface of a growing crystal in the direction opposite to that of gravitation are attained. The growth mode developed provides growth rates that are five times higher of large high-quality optical KDP crystals.     

Development of Dpa-based imidazole zinc anion receptors

A synthetic route for a new, phenolic Dpa-based aza ligand is presented and its chelation with zinc ions and imidazole were studied using UV/vis and mass spectrometry. A bathochromic shift of 30 nm was observed for the 2∗Zn complex of the ligand in UV/vis zinc titration experiments. The mass spectrum indicated formation of an imidazole anion zinc chelate complex.