Osman Çakmak

Diterpenes from the berries of Juniperus excelsa.

From the hexane extract of berries of Juniperus excelsa, one new and four known diterpenes were isolated besides a known sesquiterpene. The structures of the known diterpenes were identified as isopimaric, isocommunic, (-)ent-trans communic and sandracopimaric acids, along with the sesquiterpene 4a-hydroxycedrol and the new compound which was elucidated as 3 alpha-acetoxylabda-8(17),13(16),14-trien-19-oic acid (juniperexcelsic acid). Cytotoxic activity of the hexane extract was investigated against a panel of cell line and found highly active against LNCaP, KB-V (+VLB) and KB-V (-VLB) cell lines. Furthermore, the hexane and methanol extracts, and the new compound were found to be moderately active against Mycobacterium tuberculosis.

Cytotoxic Activity and Essential Oil Composition of Leaves and Berries of Juniperus excelsa.

ABSTRACT The composition of the water-distilled essential oils of the berries and leaves of Juniperus excelsa. M. Bieb. were analyzed by gas chromatography-mass spectrometry (GC-MS). The main components in the berries of J. excelsa., accounting for 56.1% of the oil, were determined as α-pinene (34.0%), cedrol (12.3%), L-verbenol (5.4%), and D-verbenol (4.4%) while in the leaves of J. excelsa., accounting for 63.2% of the oil, were found to be α-pinen (29.7%), cedrol (25.3%), α-muurolene (4.4%), and 3-carene (3.8%). Cytotoxic and antimicrobial potential of the berries and leaves of J. excelsa. were investigated.

Selective bromination of 1-bromonaphthalene: efficient synthesis of bromonaphthalene derivatives

Abstract Selective and specific preparation methods are described for 1,4-dibromonaphthalene, 1,5-dibromonaphthalene and 1,3,5-tribromonaphthalene. The reaction of 1-bromonaphthalene and naphthalene with stoichometric quantities of bromine by using a minimum amount of solvent (methylene chloride) at −30 and −50°C smoothly affords 1,4-dibromonaphthalene in 90% yield. Photobromination of 1-bromonaphthalene in CCl 4 at −30°C gives 1,2,3,4,5-pentabromo-1,2,3,4-tetrahydronaphthalenes, whereas 1,5-dibromonaphthalene is obtained at reflux (77°C) in 80% yield under the same conditions. Dehydrobromination of the pentabromide by t -BuOK affords 1,3,5-tribromonaphthalene as a sole product (91%). 1,5-Dibromo- and 1,3,5-tribromonaphthalenes were efficiently converted to the corresponding methoxy naphthalene derivatives.

Simple and convenient preparation of novel 6,8-disubstituted quinoline derivatives and their promising anticancer activities

A short and easy route is described for 6,8-disubstituted derivatives of quinoline and 1,2,3,4-tetrahydroquinoline from 6,8-dibromoquinolines 2 and 7 by various substitution reactions. While copper-promoted substitution of 6,8dibromide 2 produced monomethoxides 3 and 4, a prolonged reaction time mainly afforded dimethoxide 6 instead of 5, whose aromatization with DDQ and substitution reaction of dibromide 7 with NaOMe in the presence of CuI also gave rise to dimethoxide 6. Several 6,8-disubstituted quinolines were obtained by treatment of 6,8-dibromoquinoline (7) with n -BuLi followed by trapping with an electrophile [Si(Me)3Cl, S2 (Me)2, and DMF]. Furthermore, 7 was also converted to mono and dicyano derivatives. The anticancer activities of compounds 2, 7, 6, 12, 13, 15, and 16 against HeLa, HT29, and C6 tumor cell lines were tested, and 6,8-dibromo-1,2,3,4-tetrahydroquinoline (2) and 6,8-dimethoxyquinoline (6) showed significant anticancer activities against the tumor cell lines.

Photobromination of indane: preparation of bromoindenones and ready access to benzo[c]fluorenone skeleton

Abstract 1,1,3,3-Tetrabromoindane and 1,1,2,3,3-pentabromoindane were efficiently synthesized by photolytic bromination of indane. Subsequent dehydrobromination of them gave the corresponding tribromo- and tetrabromoindenes, which were easily converted to the corresponding bromoindenones by silver-supported hydrolysis. Thermolysis of 3-bromoindenone gave the benzo[ c ]fluorenone derivative.

Photooxygenation of tetramethoxybenzobarrelene : synthesis and thermal decomposition of bisdioxetane and endoperoxide

Abstract Photooxygenation of tetramethoxybenzobarrelene (2) afforded endoperoxide 4, and the diastereomeric bisdioxetanes syn,syn- and syn,anti-5 in good yields. Thermolysis of the bisdioxetane syn,syn-5 and separately of syn, anti-5 resulted in the monodioxetane trans-6 as major product, whose structure was rigorously established by X-ray analysis. On heating, the monodioxetanes trans- and cis-6 gave tetraester 7 nearly quantitatively. The homo Diels-Alder adduct 4 decomposed at room temperature to the keto ether 9 as the only isolable product. Partial photooxygenation of benzobarrelene 2 gave only the monodioxetane syn-3 , no anti-3 was observed. Monodioxetane syn-3 decomposed at room temperature to the dihydronaphthalene 8, the naphthalene derivative 10 and dimethyl oxalate. Photooxygenation of dihydronaphthalene 8, gave quantitatively the dioxetane trans-6. The activation parameters (ΔHDG, ΔSDG and ΔGDG) and excitation yields ( ΦS and ΦT) for the bisdioxetane 5 were determined by standard chemiluminescence techniques. It is concluded that the two dioxetane rings in the bisdioxetane 5 cleave thermally successively with no evidence for thermally induced intramolecular sensitization to produce upper excited state products. The mechanism of the thermal decomposition of the bisdioxetane 5 and endoperoxide 4 is discussed.

Synthesis of hydroxy, epoxy, nitrato and methoxy derivatives of tetralins and naphthalenes

Stereoselective syntheses are described for cis,trans,cis-2,3,5-tribromo-1,4-dihydroxytetralin, trans,trans,cis-2,3,5-tribromo-1,4-dihydroxytetralin, trans,trans,trans-1,4-dihydroxy-2,3-dibromotetralin, trans,trans,trans-1-hydroxy-2,3,4-tribromotetralin, cis,cis,cis-1,2-epoxy-3,5-dibromo-4-hydroxytetralin, anti-1,2:3,4-diepoxytetralin, 1-hydroxy-4-bromonaphthalene, trans,trans,trans-1,4-dinitrato-2,3-dibromotetralin, 1-nitrato-2,3,4-tribromotetralin, 2,3-dibromonaphthalene and 1-methoxy-4-nitrato-2,3-dibromonaphthalene. These isomeric arene oxides and disubstituted naphthalenes provide excellent precursors for a number of 1,4- and 2,3-disubstituted naphthalene derivatives that are difficult to prepare using other routes. The structures of the naphthalene and tetralin derivatives were assigned by NMR and other techniques.

Chemical Composition, Antioxidant, Antimicrobial and Antispasmodic Activities of the Essential Oil of Juniperus excelsa subsp. excelsa

Abstract In this study, chemical composition, antioxidant, antimicrobial and antiospasmodic activities of the essential oil of the berries Juniperus excelsa Bieb. subsp. excelsa were evaluated in vitro. GC and GS-MS analysis of the oil resulted in the identification of 25 compounds, representing 97.2 % of the oil; α-pinene (46.1 %) was the main component. Essential oil showed remarkable antimicrobial activity against the test microorganisms. The sample was also subjected to a screening for its possible antioxidant activity by using 2,2-diphenyl-l- picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. It was exhibited moderate antioxidant activity in β-carotene-linoleic acid test system. In rat ileum, J. excelsa essential oil effect was directly investigated on spontaneous contractions. It has been found that amplitude and frequency did not change significantly at all dose concentrations. Amplitude has been inhibited % 25 and frequency has been inhibited % 20 at 1 mg/mL.

Structure of exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane

The X-ray crystal structure analysis of the title compound, exo,exo-2,3-endo,endo-5,6-tetrabromobicycloheptane, C7H8Br4, which is a product of high temperature bromination of norbornadiene, shows that the skeleton of the molecule is not changed after two bromine molecules are added via successive bromination reactions. The addition of Br2 to both double bonds occurs (contrary to our expectation) in a syn fashion. It crystallizes in the orthorhombic space group Pbca with a = 15.688(2), b = 13.345(2), c = 9.461(1) Å, V = 1980.7(3) Å3, Z = 8 and Dx = 2.762 gcm−3.

Functionalisation of indene

Dibromo- and tribromoindane were synthesised by bromination of indene. Treatment of dibromo- and tribromoindane with various silver salts (silver acetate, perchlorate, sulfate and nitrate) in different solvents opened up an entry to the synthesis of various di- and tri-substituted indane derivatives.