2-Isoxazoline derivatives. Part I. A base-promoted fragmentation of 2-isoxazolines

The action of bases on 3-aryl (or alkyl)-5-acyl-2-isoxazolines has been shown to give rise to the corresponding aromatic (or aliphatic) nitriles and α-diketones by cleavage of the O-N and C₃? C₄ bonds of the heterocyclic ring. This fragmentation reaction has been extended to other 2-isoxazolines substituted in the 5-position with electron-attracting groups.     

Development and Validation of Novel DH-GC-ITMS Methods for the Determination of Freon F-141b in Formulated Polyol and Rigid Polyurethane Foam

Two efficient methods for the determination of 1,1-dichloro-1-fluoroethane (Freon F-141b) in formulated polyol and rigid polyurethane foam by dynamic-headspace-gas chromatography-ion trap-mass spectrometry were developed and validated. Rigid polyurethane foam was efficiently dissolved in dimethylformamide by heating at the temperature of 60 °C for 2 h.Validation was carried out in terms of limits of detection (LOD), limits of quantitation (LOQ), linearity, precision and recovery. LOD values of 4.00 g kg^–1 for rigid polyurethane foam and 0.73 g kg^–1 for formulated polyol were achieved, whereas linearity was statistically verified over one order of magnitude. Precision was evaluated testing two concentration levels. Good results were obtained both in terms of intra-day repeatability and between-day precision: RSD % lower than 4% (n = 6) at the concentration of 15 g kg^–1 were calculated for intra-day repeatability. Extraction recoveries up to 92.6±1.6 % (n = 3) were also calculated by the addition of Freon F-141b to the samples analysed. Both the methods were applied for the analysis of a number of formulated polyol and rigid polyurethane foam samples.     

Influence of environmental factors on composition of volatile constituents and biological activity of Helichrysum italicum (Roth) Don (Asteraceae)

The biovariability of Helichrysum italicum (Roth) Don grown wild in Calabria and Sardinia (Italy) was reported. This species has been characterized through the detection, isolation and quantitative evaluation of chemical markers (alpha-terpinolene, trans-cariophyllene and neryl acetate) by GC and GC-MS. Antioxidant activity of the methanolic H. italicum extracts using DPPH and beta-carotene bleaching test showed that the Calabrian samples were more active than those from Sardinia. The antibacterial activity of all extracts evidenced the best performance on the Gram positive bacteria particularly on Micrococcus luteus. Moreover, antifungal activity of all extracts was also tested evidencing important results particularly on the phytopathogene fungus Pythium ultimum. In general, as regards the antifungal activity, the extracts from Sardinia were more active than those from Calabria. The phytochemical analysis and the biological activity data suggested a possible use of these plant matrices in alimentary, cosmetic and pharmaceutical fields.     

Enzymatic transformation of cephalosporin C to 7-ACA by simultaneous action of immobilized d-amino acid oxidase and glutaryl-7-ACA acylase

The enzymatic transformation of cephalosporin C (CEPH C) to 7-amino-cephalosporanic acid (7-ACA) using D-amino acid oxidase (DAO) and glutaryl-7-ACA acylase (G1-7-ACA) is reported. The enzymes have been immobilized separately on different carriers, in order to maximize the catalytic activity and the stability. The reaction has been carried out in single-step-like conditions, using the two enzymes simultaneously. The effect of catalase contamination, present in the DAO preparations, was balanced by addition of extra hydrogen peroxide. In optimum conditions, the conversion of CEPH C to 7-ACA was higher than 90%, with byproduct formation lower than 4%. The mixture of immobilized enzymes was reused in repeated reaction cycles, showing an appreciable operational stability.     

Transfer reaction and molecular weight distribution in the anionic polymerization of formaldehyde

The anhydrous formaldehyde polymerization is examined. The influence of initiator and monomer concentration on the molecular weight and molecular weight distribution are emphasized. A mechanism for the transfer to the monomer is introduced. This mechanism is confirmed by experimental results and leads to the formation of formyl end groups. The influence of various initiators on the transfer reaction also is evaluated.     

Solid-phase convergent synthesis of a benzimidazolone library via the combination of two smaller arrays of carboxylic acids and secondary amines

The concept of convergent synthesis can be extended to combinatorial chemistry in order to obtain collections of products characterized by considerable chemical diversity and a certain molecular complexity. In this work, a library consisting of three carboxylic acids containing a benzimidazolonic functionality with variations at two positions was synthesized on solid phase. After cleavage, this library was combined with a second library consisting of 16 solid-supported amines containing two points of variation. IRORI technology was used for the split-and-mix synthesis of the final 48 members library.     

Sequential amination/annulation/aromatization reaction of carbonyl compounds and propargylamine: a new one-pot approach to functionalized pyridines

A general one-pot synthesis of pyridines 4a-t from the reaction of dialkyl acyclic/cyclic ketones 1a-i, methyl, aryl/heteroaryl ketones 1m-r, and aldehydes bearing alpha-hydrogens 1s,t with propargylamine 2 is described. Gold and copper salts are efficient catalysts for the reaction of ketones with 2. The formation of the pyridines 4 is suggested to proceed through the sequential amination of carbonyl compounds followed by regioselective 6-endo-dig cyclization of the N-propargylenamine (N-propargyldienamine) intermediate 3(5) and aromatization reaction. Whereas the preparation of linear polycyclic pyridine 4i can be carried out by reacting cholestan-3-one 1i with 2, the angular polycyclic pyridine 4j has been obtained starting from cholest-5-en-3-one 1j. Selectivity of the reaction of polycyclic dicarbonyls 1k,l with 2 has also been investigated.     

Copper(II) thiocyanide complexes extractable with [dibenzo-18-crown-6-K] + in chloroform

Summary Cu^II can be extracted from aqueous KSCN solutions using 2,3,11,12-dibenzo-1,7,10,13,16-hexaoxacyclooctadiene (di-benzo-18-crown-6) in CHCl₃. Raman and i.r. spectroscopies establish that the species present in the organic phase after extraction corresponds to [Cu₂OH(SCN)₅]-[dibenzo-18-crown-6-K ⁺]₂, where the Cu^II thiocyanide complex and the K⁺ crown complex are ionically associated.     

Novel approach for the rapid determination of water-soluble organic acids in wine by co-electroosmotic flow capillary zone electrophoresis

An innovative protocol for the fast analysis of some organic acids in red wine by co-electroosmotic capillary zone electrophoresis and indirect UV detection using hexadimethrine bromide (HDB) as coating agent was proposed. The adsorption of HDB onto the capillary wall provided a stable electroosmotic flow and separation of small anions was carried out using background electrolytes containing no polymer additive. Low RSD% values (<3.6%) in terms of migration times and effective mobilities were obtained from the analysis of a mixture of nitrate and nitrite and of a mixture of organic acids. An experimental design approach was used to investigate the effects of temperature, separation voltage, and percentage of methanol added to the running buffer solution on the separation of the analytes. A faster method allowing the separation of the organic acids involved in the malolactic fermentation of wine was developed. Using a running electrolyte consisting of 35% (v/v) methanol in a solution of 22 mM benzoic acid at pH 6.10 adjusted with 1.0 M TRIS-base buffer, the separation of tartaric, malic, succinic, acetic, and lactic acids was feasible in less than 210 s. Application of the method to the quantification of the above-mentioned organic acids in Italian red wine samples is reported.     

Comparative chemical composition and variability of biological activity of methanolic extracts from Hypericum perforatum L

The biovariability of Hypericum perforatum L. (St. John's Wort) grown wild in Calabria and Sardinia (Italy) was reported with the aim to characterize the species through the isolation, detection, and quantitative evaluations of chemical markers (hypericin, quercetin, rutin) by HPLC analysis. Antioxidant activity of the methanolic H. perforatum extracts showed that the Calabrian samples were more active than those from Sardinia. The antibacterial activity evidenced the best performance on the gram positive bacteria with a MIC value of 50 microg/mL. Moreover, antifungal activity of all the extracts was also tested which showed interesting results particularly on the phytopathogene fungus P. ultimum. The variability shown by the samples could be attributed to environmental factors such as chemical-physical properties, composition of the soil, geographical coordinate, altitude, and solar exposure. The phytochemical analysis and the biological activity data suggested a possible use of H. perforatum extracts in the alimentary, cosmetic, and pharmaceutical fields.