The effect of harvest periods on the chemical compositions of essential oils of sage (Salvia aucheri L.) leaves

The essential oils of sage leaves (Salvia aucheri Bentham var. canescens Boiss. & Heldr.), growing wild in South Anatolia, were extracted by hydrodistillation and analysed by GC and GC-MS. The percentage yields of the essential oils from sage leaves harvested at different years were 1.0%, 1.3%, 1.3%, 1.0%, 1.4%, 1.5% and 1.2%, respectively. In this study, 1,8-cineole, camphre, camphene α-pinene and β-pinene were identified as the major components of sage leaves collected at different periods. The main constituents of sage oil collected over the years were 1,8-cineole (35.01-48.06%), camphre (13.58-23.92%), camphene (6.77-8.82%), α-pinene (5.79-8.54%) and β-pinene (4.32-6.28%).     

Electronic structure of Li-intercalated oligopyridines: a comparative study by photoelectron spectroscopy

The role of nitrogen in the charge transfer and storage capacity of lithium-intercalated heterocyclic oligophenylenes was investigated using photoelectron spectroscopy. The development of new occupied states at low binding energies in the valence band region, as well as core level chemical shifts at both carbon and nitrogen sites, demonstrates partial charge transfer from lithium atoms to the organic component during formation of the intercalated compound. In small compounds, i.e., biphenyl and bipyridine derivatives, the position of the nitrogen heteroatom significantly affects the spacing between gap states in the Li-intercalated film; yet it has minimal effects on the charge storage capacity. In larger, branched systems, the presence of nitrogen in the aromatic system significantly enhances the charge storage capacity while the Li-N bond strength at high intercalation levels is significantly weakened relative to the nitrogen-free derivative. These observations have strong implications towards improved deintercalation processes in organic electrodes in lithium-ion batteries.     

Conformationally Homogeneous Heterocyclic Pseudotetrapeptides as Three‐Dimensional Scaffolds for Rational Drug Design: Receptor‐Selective Somatostatin Analogues

A would‐be amide : A 1,4‐disubstituted 1,2,3‐triazole was used as a surrogate for a trans amide bond to create a library of 16 diastereomeric pseudotetrapeptides as β‐turn mimetics. High‐resolution structural analysis indicated that these scaffolds adopt distinct, rigid, conformationally homogeneous β‐turn‐like structures (see example), some of which bind somatostatin receptor subtypes selectively, and some of which show broad‐spectrum activity.

     

Efficient Synthesis of New 2H‐Chromene Retinoids Hybrid Derivatives by Suzuki Cross‐coupling Reactions

In an attempt to improve anticancer activity, a series of retinoids–chromene hybrids was described. The novel heterocyclic chromene–retinoids hybrid including oxygen as a heteroatom in a six‐membered cyclic ring (2H‐chromene or 2H‐1‐benzopyran) was designed and synthesized by introducing different groups such as an aromatic or styrylphenyl ring in 6‐position of 2H‐chromene. These novel compounds were synthesized by using the efficient cascades one‐pot process involving Wittig–Horner–Emmons reaction and Suzuki–Miyaura cross‐coupling pallado‐catalyzed reactions with 60% to 90% overall yields. These new compounds were tested against glioblastoma multiforme brain cancer, medulloblastoma, neuroblastoma cell lines, and breast cancer MCF‐7 cell lines. Two of them exhibited an appreciable anti‐tumor activity in the low micromolar range, which opens new perspectives for therapeutic application on humans.     

Carbonylation of C−N Bonds in Tertiary Amines Catalyzed by Low‐Valent Iron Catalysts

The first iron catalysts able to promote the formal insertion of CO into the C?N bond of amines are reported. Using low‐valent iron complexes, including K₂[Fe(CO)₄], amides are formed from aromatic and aliphatic amines, in the presence of an iodoalkane promoter. Inorganic Lewis acids, such as AlCl₃ and Nd(OTf)₃, have a positive influence on the catalytic activity of the iron salts, enabling the carbonylation at a low pressure of CO (6 to 8 bars).     

Electrochemical response of ascorbic and uric acids at organoclay film modified glassy carbon electrodes and sensing applications

A naturally occurring Cameroonian smectite clay has been grafted with trimethylpropylammonium groups and the resulting organoclay deposited as thin film onto a glassy carbon electrode (GCE) surface. It was then exploited as a suitable matrix for the accumulation and the electrochemical detection of ascorbic acid (AA) and uric acid (UA). Cyclic voltammetry revealed an increase in oxidation peak responses along with a negative shift of the corresponding anodic peak potential for both AA and UA species when using the organoclay coated GCE in comparison with the bare electrode. The electroanalytical response was improved by coating the electrode surface with a first layer of sublimed ferrocene (FC(s)), and then overcoating with the organoclay film to avoid the mediator leaching. The resulting bilayer film exhibited good characteristics such as extended linear range and high sensitivities for AA and UA, in cyclic voltammetry and amperometry. Interestingly, the redox mediator FC(s) was likely to lower overpotentials for AA oxidation (but not for UA), making possible the selective detection of these species in a mixture. The developed method could be used for the determination of AA in a pharmaceutical preparation and for UA in urine.     

Configuration mixing involving σ and π orbitals

The effect (on the energy of the different states) of including doubly excited configurations in a - plus -configuration interaction treatment, is studied within the CNDO/2 framework. For moderately large molecules the problem of the choice of the type ( or ) of configurations taken into account is examined. When possible, comparison is made with similar non empirical calculations.

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Zusammenfassung Im Rahmen der CNDO/2 Methode wird der Einfluß (auf die Energien verschiedener Zustände) des Einschlusses doppelt angeregter Konfigurationen in einer - und -Konfigurationswechsel-wirkungs-Behandlung studiert. Für nicht allzu große Moleküle wird das Problem der Wahl der Art ( oder ) der berücksichtigten Konfigurationen untersucht. Soweit möglich, werden die Resultate mit denen ähnlicher nichtempirischer Rechnungen verglichen.

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Résumé L'effet (sur l'énergie des différents états) de l'introduction de configurations diexcitées dans une interaction de configuration plus , est étudié dans le cadre de la méthode CNDO/2. Pour des molécules de taille moyenne le problème du choix du type ou des configurations est examiné. Les résultats obtenus sont comparés aux calculs non-empirique similaires disponibles.

     

Action d'organolithiens sur la méthyl-2 quinoxaline. Etude de la réactivité des adduits

The action of organolithium reagents such as phenyllithium or n-bulyllithium on 2-methylquinoxaline gave lithiation of the methyl group which upon reaction with electtropholesphiles produce side chain alkenyl derivatives. On the other hand organolithium reagents react with the quinoxaline azomethine bond to give I-lithio-2-alkyl)or ary-1)-3 methylquinoxalines which can be further loithiated on the methyl group to give 2-alkyl(or aryl)-3-alkenylquinoxaline derivatives. The adducts can be condensed with clectrophiles such as benzonitrile or methlyl benzoate but only methyl benzoate leads to N condensed derivatives. Furthermore substituted 1,2,3,4-terahydroqinoxalines are available via the above lithio intermediates.     

Mechanism of the Radical Copolymerization of Methyl Methacrylate and Maleic Anhydride

The kinetics of the copolymerization of methyl methacrylate and maleic anhydride was investigated in benzenic solutions at 60 and 70° C and in bulk at 60°C. The microstructure of the copolymers was determined by ¹H-NMR and IR spectrophotometry. In benzene solutions the mechanism of copolymerization involves the participation of an associative species between both comonomers. In bulk a terminal model is sufficient to explain all the results.