Enthalpy of polymerisation of endo-2-methyl-7-oxabicyclo[2.2.1]heptane

The enthalpy of combustion of poly(oxy-2-methyl-1,4-cyclohexenylene) prepared from endo-2-methyl-7-oxabicyclo[2.2.1]heptane has been determined by oxygen-bomb combustion calorimetry. The calculated standard enthalpy of formation of the polymer, ΔH (298,15K)= —283,5±3,0 kJ (base-mol)^—1, has been combined with that of the monomer to give the enthalpy of polymerisation of liquid monomer to solid polymer as ΔH = —33,3±3,7 kJ mol^—1.     

Enthalpy of polymerisation of 7-oxabicyclo[2.2.1]heptane,and exo- and endo-2-methyl-7-oxabicyclo[2.2.1]heptane

The enthalpies of combustion of poly(oxy-1,4-cyclohexylene) formed from 7-oxabicyclo[2.2.1]heptane ( 1 ) and of its derivatives formed from exo- and endo-3-methyl-7-oxabicyclo[2.2.1]heptane ( 2a and 2b ) have been measured. From literature values for the enthalpies of combustion of the liquid monomers, the enthalpies of polymerisation have been derived: ?ΔH(1→c)=44,3±1,9, 49,7±2,6, and 45.4±3,1 kJ mol^?1, respectively. The results indicate a minimum strain energy in these polymers of ca. 15 kJ mol^?1. The estimated entropies of polymerisation yield ceiling temperatures of 320, 240, 200°C respectively for the three bicyclic ethers.—The reasons for the discrepancy between our present ?ΔH(1→c) for the endo compound and that previously reported², are explained.     

Enthalpy of polymerisation of ethylene oxide and of copolymerisation of ethylene oxide with 7-oxabicyclo[2.2.1]heptane

The enthalpies of combustion of poly(ethylene oxide), ΔH(c)=-1178,7 ± 1,3 kJ . mol^-1, and of a random copolymer of overall molar composition 0,41 (poly(ethylene oxide)) + 0,59 (poly(oxy-1,4-cyclohexylene)), ΔH(c)=-2566,4 ± 1,8 kJ . mol^-1, were measured at 298,15 K by high-precision bomb calorimetry. The enthalpy of polymerisation of ethylene oxide was derived as ΔH (l → c) = -102,4 ± 1,6 kJ . mol^-1. The enthalpy of copolymerisation of ethylene oxide and 7-oxabicyclo[2.2.1]heptane was ΔH (l → c) = -63,0 ± 2,1 kJ . mol^-1, compared with -68,1 ± 1,6 kJ . mol^-1 for producing the two homopolymers in the proportion in which the monomers were present in the copolymer. It is concluded that insertion of an ethylene oxide unit into a poly(oxy-1,4-cyclohexylene) chain does not affect the strain-energy by a significant amount.     

Enthalpy of polymerisation of 2-oxabicyclo[2.2.2]octan-3-one

The enthalpies of combustion of crystalline 2-oxabicyclo[2.2.2]octan-3-one ( 1 ), and five different crystalline poly(oxycarbonyl-1,4-cyclohexylene) samples formed from 1 were measured at 298, 15 K by high-precision bomb calorimetry. For 1 , the enthalpies of combustion and of formation were, ?ΔH(c) = 3717,5 ± 1,3 kJ·mol^?1 and ?ΔH(c) = ? 466,2 ± 1,6 kJ·mol^?1. After correction for the presence of n-butyl- or tert-butoxy-end groups in the polyester samples, a consistent enthalpy of polymerisation of 1 was obtained, ΔH(c → c) = ? 20,9 ± 2,3 kJ·mol^?1. The enthalpy of sublimation of 1 was measured, ΔH (1) = 69,6 ± 2,1 kJ·mol^?1; the value for the polyester unit was derived as 49 kJ·mol^?1.     

Synthesis and cationic ring-opening polymerization of 2-methylene-7-oxabicyclo[2.2.1]heptane

A new unsaturated bicyclic ether, 2-methylene-7-oxabicyclo[2.2.1]heptane ( 4 ) was synthesized by successive Diels-Alder addition of furan to acrylonitrile, hydrogenation of cyano compound 5 , and Hofmann degradation of the quaternary ammonium hydrate 7 derived from the amine 6 . Cationic polymerization of the monomer 4 was carried out in CH₂Cl₂ using BF₃ · OEt₂, PF₅, SbCl₅ and SnCl₄ as catalysts in the temperature range of ?20 to ?25°C. White or slightly yellow powdery polymers of low molecular weight were obtained with PF₅ and BF₃ · OEt₂ as catalysts, while no polymer was obtained with SbCl₅ and SnCl₄ as initiators. The IR, ¹H and ¹³C NMR spectra of the polymers indicated that they consist of three kinds of repeating units, that is, two unsaturated units caused by ring-opening polymerization and one addition unit. Using proton NMR data of the polymers, the distribution of repeating units was calculated. A polymerization mechanism is proposed. The thermal stability of the obtained polymers is discussed.     

Polymerization of cis- and trans-8-oxabicyclo[4.3.0]nonane

The polymerization of cis- and trans-8-oxabicyclo[4.3.0]nonane in bulk was investigated with PF₅ as initiator. The trans-isomer polymerizes very readily to high polymers (M?_w up to 200 000), whereas the cis-isomer under identical conditions fails to polymerize. This difference in behavior is attributed mainly to the fact that the strain in the trans-isomer is much higher than in the cis-isomer. The polymerization results with the trans-isomer for the temperature interval of ?25 to 75°CC are interpreted in terms of propagation/depropagation reactions via an oxonium ion mechanism and a concurrent chain breaking reaction which is noticeable by the decrease in molecular weight with time. The polymerization systems are not reversible with changing temperature and the data indicate that at the upper end of the temperature interval there is a deactivation, which was investigated. Copolymerization of the cis- and trans-isomers shows that the cis-isomer is reactive in the presence of the trans-isomer. The molecular weight of the polymers decreases with increasing cis-isomer content in the feed.     

Polymerization of bicyclic acetals, 4. Cationic polymerization of 1,3,3-trimethyl-2,7-dioxabicyclo[2.2.1]heptane

The polymerization of 1,3,3-trimethyl-2,7-dioxabicyclo[2.2.1]heptane ( 1 ) was carried out in methylene chloride, toluene, and 1-nitropropane at temperatures between ?78 and 0°C. Borontrifluoride etherate, triethyloxonium tetrafluoroborate, antimony pentachloride, and iodine were used as initiators. Irrespective of the solvents and initiators used, the products at 0°C were white powders with melting points of 50—55°C, while those obtained at lower temperatures were sirups. The number average molecular weights of the unfractionated products ranged from 400 to 600. The molecular weight distribution of the oligomers prepared at 0°C was broad, in contrast to the relatively narrow distribution for those obtained at ?40°C. On the basis of the determination of the hydroxyl group and unsaturated bond of the oligomers, along with the hydrogenolysis of 1 , the structure of the oligomers and the mechanism of their formation are discussed.     

Synthesis and anticonvulsant activity of 7-alkoxy-triazolo-[3, 4-b]benzo[d]thiazoles

The present study describes the chemical synthesis and anticonvulsant activity evaluation of a series of 7-alkoxy-triazolo-[3, 4-b]benzo[d]thiazoles. Most compounds exhibited good anticonvulsant activity in the Maximal electroshock (MES) test. And the structure-activity relationships (SAR) were analyzed. Among the compounds studied, 7-octyloxy-triazolo-[3, 4-b]benzo[d]thiazole (5g) was found to be the most potent compound with a median effective dose (ED(50)) value of 8.0 mg/kg and a protective index (PI) value of 15.0, possessing better anticonvulsant activity and higher safety than marketed drugs carbamazepine and phenytoin. The mechanism study of compound 5g showed that it displayed broad spectrum activity in several models, and it is likely to have several mechanisms of action (including inhibiting voltage-gated ion channels and GABAergic activity).     

Percutaneous absorption of 7, 10 14C-benzo[a]pyrene and 7, 12 14C-dimethylbenz[a]anthracene in mice

The percutaneous penetration, tissue distribution and excretion of 14C-labeled benzo[a]pyrene (BP) and dimethylbenz[a]anthracene (DMBA) were studied in mice. Both BP and DMBA rapidly penetrated the skin and were excreted more in the feces than in the urine. The proportion of BP and DMBA absorbed was less with increasing applied dose due to apparent saturation of the uptake process. Uptake from the dorsal skin of the nose was similar to uptake from the dorsal nuchal skin.     

Synthese neuer pseudoleiterpolymere mit 7H-benzimidazo[2,1-a]benzo[d,e]isochinolin-7-on-3,11-diyl-einheiten in der hauptkette

A series of novel semi-ladder polymers containing 7H-benzimidazo[2,1-a]benzo[d,e]isoquinolin-7-on-3,11-diyl units in the chain was prepared by one-step high temperature solution polycondensation of 4,4′-oxy-,4,4′-carbonyl-, and 4,4′-sulfonyldi-1,8-naphthalenedicarboxylic anhydride ( 1a - c ) with 2,2′-diamino-4,4′-oxydianiline ( 2 ) or 2,2′-diamino-4,4′-hexafluoroisopropylidenedianiline ( 4 ). The similarity of the IR and UV spectra of the polymers and the model compounds 7 a- c confirms the presence of the benzimidazobenzoisoquinolinone rings in the polymer chain. All the resulting polymers have excellent thermal stability both in argon and in air. The polymers prepared from 4 are soluble in 1-methyl-2-pyrrolidone and phenol/1,1,2,2-tetrachloroethane.     

Aqueous ring-opening metathesis polymerisation of 7-oxanorbornene derivatives with oxygen-containing functionalities

A number of 7-oxanorbornene derivatives with hydroxymethyl, methoxymethyl and acetoxymethyl functionalities were synthesised and investigated as monomers in ring-opening metathesis polymerisation (ROMP) catalysed by commercial ruthenium trichloride in aqueous ethanolic solvents. Comparison was made with related polymerisations of 7-oxanorbornene derivatives with anhydride, methoxymethyl and carboxylic acid functionalities. The structures of the polymers were investigated by ¹H and ¹³C NMR and their molar masses and molar mass distributions by gel-permeation chromatography.     

Synthesis and characterization of lithium and magnesium complexes based on [EDTA][PEG400]2 and [EDTA]3[PEG400]7

Two distinct types of host polymers, [EDTA]₃‐[PEG400]₇ and [EDTA][PEG400]₂, consisting of polyether chains linked together by ethylenediaminetetraacetic acid (EDTA) chelating units, were synthesized from EDTA acetate esters and poly(ethylene glycol) 400 (PEG400). Their structures were revealed by analytical analyses, viscosimetric measurements, NMR and FT‐IR studies. Direct dissolution of δ‐LiCl and δ‐MgCl₂ in these prepared host polymers resulted in the following complexes: [EDTA]₃‐[PEG400]₇/(LiCl)_6.39, [EDTA]₃[PEG400]₇/(MgCl₂)_8.23, [EDTA]₃[PEG400]₇/(LiCl)_6.39(MgCl₂)_6.16, [EDTA][PEG400]₂/ (LiCl)_2.26, [EDTA][PEG400]₂/(MgCl₂)_1.98 and [EDTA]‐[PEG400]₂/(LiCl)_2.26(MgCl₂)_1.98. Mid‐ and far‐FT‐IR spectroscopic studies revealed the following properties for all six complexes: a) the polyether chains are in the trans–gauche–trans conformation; b) the Mg²⁺ ion could be hexa‐ or heptacoordinated to the chelating sites of EDTA; c) the Li⁺ ion is preferentially coordinated by the oxygen atoms of the residual acetate groups and polyether moieties. Results of conductivity measurements at room temperature indicated that the proposed Mg products might be very useful for the development of electrochemical transducers for measuring water hardness.

Esterification of EDTA dianhydride with PEG400; (2): Synthesis of the complexes (MX_n = LiCl/MgCl₂).     

Assessment of Immunomodulatory Activities and in vitro Toxicity of New Quinolone 7-ethyl 9-ethyl-6-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-h]quinoline-7-carboxylate

Our previous studies on leukemia cells L1210 and cervical cancer HeLa cells revealed cytotoxic effects of the 7-ethyl 9-ethyl-6-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-h]quinoline-7-carboxylate (E2h), a new synthetically prepared quinolone derivative, toward selected cancer cell lines. The aim of the present study was to examine the cytotoxicity of E2h toward next cell lines and tissues; that is, human cancer HL-60 and A549 cells, human non-cancer fibroblast BHNF-1 cells, and reconstructed human epidermis tissues. Further we investigated the immunomodulatory activity of E2h on murine macrophage RAW 264.7 cells. Selenadiazoloquinolone E2h induced specific antiproliferative/cytotoxic activity against leukemia HL-60 cells and is the potent inducer of apoptotic cell death. Quinolone derivative demonstrated the immunomodulatory activities on RAW 264.7 cell line murine macrophages. The immunobiological studies revealed time- and concentration-dependent effective immunomodulation of pro- and anti-inflammatory cytokines’ release and antiproliferative/cytotoxic effect following exposure of RAW 264.7 cells to E2h.

Abbreviations: DMEM, Dulbecco’s modified eagle medium; DMSO, Dimethylsulfoxide; EtBr, Ethidium bromide; PI, Propidium iodide; E2h, 7-ethyl 9-ethyl-6-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-h]quinoline-7-carboxylate.     

On the mechanism of polymerization of methyl substituted 7-oxabicyclo-[2.2.1]-heptanes

The polymerization of endo- and exo-2-methyl-7-oxabicyclo-[2.2.1]-heptane with phosphorus pentafluoride catalyst in methylene dichloride and nitrobenzene has been found to proceed with increasing yield and molecular weight with decreasing temperature in the range +25°C to ?30°C, but at ?78°C there was no polymerization. The ring-opening appears to proceed exclusively through nucleophilic attack at C-1 in the alkyloxonium ion, leading to only one type of structural unit in each type of polymer. The polymers of the exo-2-methyl isomer are completely soluble in THF, whilst those of the endo-2-methyl isomer are insoluble. The solubility appears to be connected with flexibility of the chain molecule associated with the possibility for interconversion between different chair conformations for the cyclohexane ring-structures. By ring-closure of 2.6-dimethylcyclohexane-(1.4)-diol two isomers have been prepared and identified. The endo,exo-2.6-dimethyl-7-oxabicyclo-[2.2.1]-heptane gives insoluble, highly crystalline polymers with phosphorus pentafluoride catalyst in methylene dichloride. The failure of the corresponding exo,exo-2.6-dimethyl isomer to polymerize under identical conditions is explained by conformational analysis.     

[Met5]enkephalin-Arg6-Phe7- and [Met5]enkephalin-Arg6-Gly7-Leu8-immunoreactive nerve fibres and neurons in the superior cervical ganglion of the rat

[Met⁵]enkephalin-Arg⁶-Phe⁷- (MEAP-) and [Met⁵]enkephalin-Arg⁶-Gly⁷-Leu⁸- (MEAGL-) immunoreactivity was studied by indirect immunohistochemistry in the superior cervical ganglion of the rat with specific antisera produced in rabbits against the corresponding synthetic opioid peptides. Several MEAP- and a few MEAGL-immunoreactive principal nerve cells were observed in the ganglion, while the small intensely fluorescent cells appeared as non-reactive. The superior cervical ganglion also contained dense networks of MEAP- and MEAGL-immunoreactive nerve fibres, which often formed basket-like structures around the principal nerve cells and small intensely fluorescent cells. After ligation of the preganglionic nerve trunk with simultaneous transection of the main postganglionic trunks, a distinct accumulation of both MEAP- and MEAGL- immunoreactivity was observed on both sides of the ligature. Ligation of the preganglionic nerve trunk caused a marked decrease in the number of both MEAP- and MEAGL-immunoreactive nerve fibres in the ganglion. Ligation of the main postganglionic nerve trunks with simultaneous preganglionic nerve division resulted in accumulation of MEAP- and MEAGL-immunoreactive material on the ganglionic side of the ligature in both the external and internal carotid nerve. After division of both the pre- and postganglionic nerve trunks, some immunoreactive nerve fibres and principal nerve cells were still observed in the ganglion. A few immunoreactive neurons and nerve fibres were also observed in the ganglion stellatum. A large number of MEAP- and MEAGL-immunoreactive nerve fibres was detected in the spinal cord at the levels C6-Th6. A few neurons in the intermediolateral cell column of the spinal cord at levels C8-Thl showed MEAP- but not MEAGL-immunoreactivity. The cultured superior cervical ganglion contained a few MEAP-immunoreactive neurons, and the fibre outgrowth showed immunoreactivity both to MEAP and MEAGL. In electron microscopy, MEAGL-immunoreactivity in the superior cervical ganglion was localized in nerve fibres containing neurotubules and in principal nerve cells.The present results demonstrate that the rat superior cervical ganglion contains both extrinsic and intrinsic MEAP- and MEAGL-immunoreactive nerve fibres. Most of these fibres are of preganglionic origin. Both the principal nerve and small intensely fluorescent cells are often surrounded by MEAP- or MEAGL-immunoreactive nerve fibres and may receive innervation by these fibres. Several ganglionic neurons projecting to the sympathetic target tissues show MEAP- and/or MEAGL-immunoreactivity. Since MEAP- and MEAGL sequences are included in the proenkephalin A molecule, but not in the other opioid precursor molecules, it is evident that a neuronal system containing proenkephalin-A-derived enkephalins, is present in the rat superior cervical ganglion.     

Bovine rotavirus strain 678 possesses VP4 of serotype P7[5] specificity

Summary.  Bovine rotavirus strain 678 is the first G8 strain of bovine origin but the literature is confusing as to its P type. In this study, two-way cross neutralization between 678 and 0510, a prototype G6P7[5] virus, was shown by plaque-reduction neutralization assays, establishing the P type of 678 as being P7[5]. The P7[5] specificity of 678 VP4 was reinforced by the finding that the VP8^* portion of 678 VP4 had the highest amino acid identity with those of P7[5] bovine rotaviruses. Apparent contradiction with previous serological studies relates to intricacy of antigenicity and immunogenicity of UK VP4 in reassortants. Received October 28, 1996 Accepted January 6, 1997