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N-Acetyllactosamine is a common saccharide motif found in various biologically active glycans. This motif usually works as a backbone for additional modifications and thus significantly influences glycan conformational behavior and biological activity. In this work, we have investigated the type-2 N-acetyllactosamine scaffold using the complete series of its monodeoxyfluorinated analogs. These glycomimetics have been studied by molecular mechanics, quantum mechanics, X-ray crystallography, and various NMR techniques, which have provided a comprehensive and complete insight into the role of individual hydroxyl groups in the conformational behavior and lipophilicity of N-acetyllactosamine.

The Tn antigen (GalNAcα1-Thr/Ser) is abundantly expressed in many tumors but rarely found in healthy tissues, which makes it an attractive epitope for antitumor immunotherapy. The use of the Tn antigen in the development of therapeutic antitumor vaccines is hampered by its low immunogenicity, which may be enhanced by deoxyfluorination of the GalNAc moiety. Here, we report the synthesis of protected 3- and 4-fluoro analogues of the threonine-containing Tn antigen. As the stereoselective synthesis of α-linked fluorinated GalNAc is difficult, we prepared a panel of C3 and C4 deoxyfluorinated galactosazide thiodonors and evaluated their stereoselectivity in the glycosylation of carbohydrate acceptors and threonine derivatives. Glycosylation of threonine derivatives with O-benzylated C4 fluoro donors gave only modest but usable α-selectivity of α/β = 2.5–3/1. The use of acyl and silyl protection at the 3- and 6-positions of the C4 fluoro donors did not enhance the selectivity. Installing a 4,6-di-tert-butylsilylene-protecting group in C3 fluoro donors resulted in exclusive α-selectivity and reaffirmed the strong α-directing effect of this protective group in glycosylation with galacto-configured glycosyl donors.

Mo, CoMo and NiMo sulfide catalysts were prepared using MgO, Al2O3, ZrO2, TiO2, MCM-41 and activated carbon supports. The catalysts were tested in parallel hydrodeoxygenation (HDO) of octanoic acid and hydrodesulfurization (HDS) of 1-benzothiophene. For all supports, NiMo catalysts were more active in both HDO and HDS than Mo and CoMo catalysts. HDO activity of NiMo catalysts decreased with type of support in the following order TiO2> C > ZrO2> Al2O3> MCM-41 > MgO. The products of HDO were linear C7 and C8 hydrocarbons. Some isomerization and cracking activity was observed only with MCM-41 support. HDS activity of NiMo catalysts decreased in the following order C > ZrO2> TiO2> Al2O3> MgO > MCM-41. HDO/HDS selectivity was influenced by the active phase and the support type and it was the highest over the NiMo/TiO2catalyst.

Control of anomeric stereoselectivity in glycosylation with deoxofluorinated glycosyl donors is critical for assembly of fluorinated oligosaccharides. Here, we report the synthesis of benzylated 3-fluoro and 4-fluoro analogues of phenyl 1-thioglucosazide and galactosazide donors and evaluation of their stereoselectivity in glycosylation of a series of model carbohydrate acceptors using the Tf2O/Ph2SO promoter system. Low-temperature NMR revealed formation of covalent α-triflate and both anomers of oxosulfonium triflates under selected glycosylation conditions. This study demonstrates how the stereoselectivity depends on acceptor reactivity and glycosyl donor configuration. Reactive acceptors favor formation of 1,2-trans-β-glycosides with both d-glucoand d-galactodonors, whereas poorly reactive acceptors favor formation of 1,2-cis-α-glycosides with d-galactodonors but are unselective with d-glucodonors.

In the study of the simultaneous hydrodesulfurization of 1-benzothiophene and the olefin hydrogenation of 1-methylcyclohex-1-ene (1-MCH), we encountered a rearrangement of 1-MCH during the first step of catalytic hydrogenation, which yielded various branched cyclic olefins; mainly ethylcyclopentene and dimethylcyclopentene isomers. The volatile isomerization products were isolated directly from the diluted reaction mixture via the combination of chromatographic techniques including preparative gas chromatography, and were undoubtedly assigned by NMR spectroscopy. The precise identification of the isomerization products was required for a detailed kinetic study.

AbstractExtracts from savory (Satureja hortensisL.) and thymus (Thymus vulgarisL.) were obtained by supercritical fluid extraction, hydrodistillation, and Soxhlet extraction with benzene and ethanol. The composition of volatile compounds in the extracts was determined by gas chromatography, and the toxicity and antifeedant effects of the extracts on larvae of Colorado potato beetle were evaluated.Generally it is possible to claim that all extracts caused mortality in 24 h after their topical application. Significant differences between the particular extracts and plants were found.The most effective isolates were the essentials oils which showed the lowest LD50. The lethal dosages of 22 mg and 29 µg were determined for oil from S. hortensisand T. vulgaris, respectively, but the difference was not Significant (P < 0.05). The extracts of S. hortensis(SFE2 and SFE3) had similar efficiencies as the oils with lethal dosages of LD5028 µg and 30 µg, respectively.Strong deterrent effects of all extracts against larvae were observed. In the no-choice test with leaf discs, the consumption of control food by the fourth instars larvae L. decemlineatawas Significantly higher than the consumption of treated food in the treatment concentrations (P < 0.05). The AFI declined depending on the concentration.

Background, Aims and Scope: In the first part of this paper the main principles which control the dehalogenation of polychlorinated aromatic compounds on municipal waste incineration fly ash (MWI-FA) have been discussed and the model fly ash of similar dehalogenation activity has been proposed. Even if both systems show comparable dehalogenation properties, the main question concerning the postulated identical reaction mechanism in both cases is left unanswered. The other very important point is to what extent is this dechlorination mechanism thermodynamically controlled. The same problem is often discussed in the literature also for the de novosynthetic reactions. From the data it is clear that metallic copper plays a decisive role in the mechanism of the dehalogenation reaction. Although the results reported in the first part strongly support the idea that copper acts in this dechlorination as the reaction component, in contrast to its generally accepted catalytic behaviour, we believed that additional support for this conclusion can be obtained with the help of a thermodynamic interpretation of the mechanism of the reaction. Results and Discussion: The pathways of hexachlorobenzene dechlorination on MWI-FA and model fly ash were studied in a closed system at 260-300°C under nitrogen atmosphere. These pathways were the same for both systems, with the following prevailing sequences: hexachlorobenzene → pentachlorobenzene → 1,2,3,5-tetrachlorobenzene → 1,3,5-trichlorobenzene → 1,3-dichlorobenzene. Thermodynamic calculations were carried out by using the method of minimization total Gibbs energy of the whole system. In the calculations, the following reaction components were taken into account: all gaseous chlorinated benzenes, benzene, hydrogen chloride, a gaseous trimer Cu3Cl3, and also Cu2O and CuCl2as solid components. The effect of the reaction temperature and the amount of copper and water vapour were considered as well. The effect of reaction temperature was determined from the data calculated for the 500 to 750 K temperature region. The effect of the initial composition was determined for the molar amounts of copper = 0.01-3 moles and water vapour = 0.2 to 3 moles per mole of chlorobenzene isomer. Conclusions: The results of hexachlorobenzene dechlorination by MWI-FA and model fly ash under comparable reaction conditions allow us to conclude that both dechlorinations proceed via the same dechlorination pathways, which can be taken as an evidence of the identical dehalogenation mechanism for both systems. The relative percentual distribution of the dehalogenated products depends on the temperature, but not on the initial amount of water vapour or copper metal. On the other hand, the initial amount of copper substantially affects the conversion of the dehalogenation as well as the molar ratio of Cu3Cl3to HCl in the equilibrium mixture. Comparison of the experimental with thermodynamic results supports the idea that dehalogenation reactions are thermodynamically controlled. Recommendations and Outlook: Thermodynamic analysis of the dehalogenation reactions may prove useful for a wide range of pollutants. The calculations concerning polychlorinated biphenyls and phenols are under study.

Background, Aims and Scope: It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450°C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash matter therefore plays the decisive role. In the present paper, the function of important components responsible for the dehalogenation activity of MWI-FA is analysed and compared with the model fly ash. Methods: With the aim of accounting for the dehalogenation activity of MWI-FA, the following studies of hexachlorobenzene (HCB) dechlorination were performed: The role of copper in dehalogenation experiments was evaluated for five types of metallic copper. The gasification of carbon in MWI-FA was studied in the 250-350°C temperature range. Five different kinds of carbon were used, combined with conventional Cu° and activated nanosize copper powder. The dechlorination experiments were also carried out with Cu(II) compounds such as CuO, Cu(OH)2, CuCl2and CuSO4. The results were discussed from the standpoint of thermodynamics of potential reactions. Based on these results, the model of fly ash was proposed, containing silica gel, metallic copper and carbon. The dechlorination ability of MWI-FA and the model fly ash are compared under oxygen-deficient atmosphere. Conclusions: The results show that, under given experimental conditions, copper acts in the dechlorination as a stoichiometric agent rather than as a catalyst. The increased surface activity of copper enhances its dechlorination activity. It was found further that the presence of copper leads to a decrease in the temperature of carbon gasification. The cyclic valence change from Cu° to Cu+ or Cu2+is a prerequisite for the dehalogenation to take place. Recommendation and Outlook: Thermodynamic analysis of the dechlorination effect, as well as the comparison of dechlorination pathways on MWI-FA and model fly ash, can provide a deeper understanding of the studied reaction.

Well defined E/Z isomers of N-methoxy-p-nitrobenzimidoyl chloride, N-methoxybenzimidoyl chloride, methyl N-methylbenzohydroximate and ethyl N-hydroxybenzimidate were prepared in order to provide model data for studies of benzhydroximic acid derivatives and related compounds. NMR parameters [¹H, ¹³C and ¹⁵N chemical shifts and ¹J(¹³C, ¹³C) coupling constants] were determined. The results show that stereochemically most significant are the values of ¹J(¹³C, ¹³C) couplings between aromatic Cipso and C&dbond;N carbons and that the relationship, |Jcis| > |Jtrans|, known for this coupling from oximes, is not affected by electronegative substituents at the C&dbond;N carbon atom, but the values are. Copyright © 2002 John Wiley & Sons, Ltd.