67 research outputs found
Selective pyrone functionalization: reductive alkylation of triacetic acid lactone
No full textThe one-pot reaction of aldehydes, triacetic acid lactone, and Hantzsch 1,4-dihydropyridine affords 3-alkyl pyrones via a reductive alkylation strategy.This is a manuscript of an article published as Kraus, George A., Kevin Basemann, and Tezcan Guney. "Selective pyrone functionalization: reductive alkylation of triacetic acid lactone." Tetrahedron Letters 56, no. 23 (2015): 3494-3496. 10.1016/j.tetlet.2015.01.141. Posted with permission.</p
Heterocycles from wine: synthesis and biological evaluation of salidrosides
No full textWine is composed of a variety of tannins, of which a sub-class includes salidrosides, which are largely uninvestigated compounds. The first syntheses of galloylated salidrosides are reported in 7 steps from commercially available starting materials through a platform approach. The antimicrobial activity of the salidrosides against Escherichia coli strains is described.This is a manuscript of an article published as Guney, Tezcan, Stephanie A. Kohles, Victoria L. Thompson, Gregory J. Phillips, and George A. Kraus. "Heterocycles from wine: synthesis and biological evaluation of salidrosides." Tetrahedron 71, no. 20 (2015): 3115-3119. DOI: 10.1016/j.tet.2014.08.065. Posted with permission.</p
Efficient synthesis of fluorescent rosamines: multifunctional platforms for cellular imaging
No full textSubstituted rosamines are efficiently prepared through a new organometallic addition to an imine-substituted xanthone as a novel primary amine equivalent. The synthesis reduces the number of synthetic steps to the targeted rosamines, for convenient and facile access to potential libraries of rosamine dyes. The prepared rosamine derivatives represent unique multifunctional platforms that possess radiolabeling capability and fluorescence. Rosamines have (i) useful non-specific binding properties in mammalian cells and plant root hair, and (ii) positive uptake or binding properties in microbial systems.This is a manuscript of an article published as Kraus, George A., Tezcan Guney, Aaron Kempema, Joel M. Hyman, and Bahram Parvin. "Efficient synthesis of fluorescent rosamines: multifunctional platforms for cellular imaging." Tetrahedron Letters 55, no. 9 (2014): 1549-1551. DOI: 10.1016/j.tetlet.2014.01.067. Posted with permission.</p
Islamic issues in studies on Muslims in Germany
No full textTezcan L. Das Islamische in den Studien zu Muslimen in Deutschland. Literaturbericht. Zeitschrift für Soziologie. 2003;32(3):237-261.Due to its international importance Islam has become a very desired object of the scholarly studies. The current interest in Islam reminds us of El Dorado. This article aims at providing orientation in the jungle of fieldwork-based studies regarding the subject of Islam/Muslims in Germany. One crucial point in the scholarly work is the attempt to position Islam in relation to modernity. The question is quickly translated into politics: are Muslims able and willing to be integrated? This report on the academic literature wants, for one, to give an overview of the main approaches. At the same time, some empirical results will be presented. In addition, attention is directed to problems with this research. The difficulties are mostly based on interpretations that too quickly attempt to view Muslims in terms of theories of modernization and individualization. At the same time, this indicates that the cultural background of the researchers may have implications of its own for the interpretations suggested. The author pleads finally to consider the contemporary effects of modernity and the obstinacy of religious patterns in a common framework without reducing either to the other
Synthesis of biologically active polycyclic natural products and multifunctional imaging probes
No full textNatural products with their ever-growing potential applications in the drug discovery process have influenced many researchers to devise flexible and concise synthetic strategies towards these biologically active substances. As more complex and structurally unique natural products are isolated from plants or microorganisms, developing innovative synthetic tools become highly desirable to obtain them in sufficient quantities. Synthetic organic chemistry allows a thorough investigation of their biological properties and the endeavor enhances the dynamic evolution process of the field. With this in mind, we have developed new synthetic methodologies to synthesize meroterpenoid paracaseolide A and an important class of 3-methylcarbazole alkaloids. In addition, the same approach enabled a direct synthesis of fluorescent rosamine probes with practical applications.
The first chapter of the dissertation describes the total synthesis of potential anti-cancer agent (±)-paracaseolide A, which possesses a unique tetracyclic framework with concave and convex faces. The facile synthesis of the natural product was accomplished in 8 steps in 6.6% overall yield, utilizing multiple sulfoxide eliminations and a key tandem 1,4-conjugate addition/aldol reaction to introduce the necessary functional groups onto the tetracyclic bis-lactone scaffold. The synthetic strategy allows diverse analogue development through a common advanced intermediate.
The second chapter reveals a novel inverse electron-demand Diels-Alder (IEDDA) methodology to access biologically active and naturally-occurring 3-methylcarbazoles as well as synthetic derivatives using 3-chloroindoles and the 2-pyrone methyl coumalate. The transformation constitutes the first successful example of its kind; consequently extending the scope of indole dienophiles in the IEDDA reactions. The application of the single-pot Diels-Alder/decarboxylation/elimination domino sequence resulted in the metal-free generation of carbazole alkaloids with exclusive regioselectivity in up to 90% yield.
The last chapter focuses on the synthesis of rosamine probes to capitalize on a new strategy of an organolithium addition to a benzophenone imine-substituted xanthone. Subsequent acid-catalyzed deprotection and dehydration resulted in an efficient four-step synthesis from 3,6-dihydroxyxanthone. The condensed synthetic approach provides rapid access to desirable primary amine-functionalized multifunctional rosamine analogues in good yields for applications in live-cell imaging.</p
Phytocoris (Exophytocoris) carapezzai Çerçi & Koçak & Tezcan 2019, sp. nov.
No full text<i>Phytocoris</i> (<i>Exophytocoris</i>) <i>carapezzai</i> sp. nov. <p>(Figs 2, 5A)</p> <p> <b>Type locality.</b> Turkey, Karaman, Merkez, 37°13′18.3″N 33°13′14.2″E.</p> <p> <b>Material examined.</b> HOLOTYPE: 1 3 (AZMM), <b>TURKEY: KARAMAN:</b> Merkez, 37°13′18.3″N 33°13′14.2″E, 8.ix.2015; glued on a pointed cardboard with male genitalia on the same cardbord, labelled as follows: ʻTurkey, Karaman prov. / Merkez, with UV light trap / Ö. Koçak coll. [white printed label] // Holotypus / <i>Phytocoris</i> (<i>Exophytocoris</i>) <i>carapezzai</i> sp. n. / B. Çerçi det. 2019 [red printed label]’. PARATYPES: <b>TURKEY: KARAMAN:</b> 2 33, Merkez, 8.ix.2015, light trap, Ö. Koçak leg., B. Çerçi det. (BCIT).</p> <p> <b>Diagnosis.</b> The new species is recognized by the combination of the following characters: general coloration yellowish brown, pronotum darker than hemelytra and scutellum. First antennal segment white with dense red patterns, eyes very big, ocular index 0.6–0.8 in male. Posterior margin of pronotum with narrow white marginal band and wavy and uninterrupted brown submarginal band. Hemelytra with scattered reddish pattern, tip of clavus darkened, outer margin of corium and inner margin of cuneus with red dots interrupted by white coloration along their whole length, inner upper corner of cuneus with isolated red dot. Membrane brownish and translucent with dense small pale patches. Femora (Fig. 2B) dark brown with dense white dots. Left paramere edentate (Fig. 2E), hypophysis strongly enlarged before apex, vesica with marginally dentate lamellae apically (Fig. 2D), sclerotized process of vesica (Fig. 2C) stick-like, long and thick, edentate and slightly bent towards apex.</p> <p> <b> Description. Male. <i>Coloration.</i></b> General coloration yellowish brown (Fig. 2A). Head yellowish brown with reddish patterns. First antennal segment whitish, maculated in red, second antennal segment yellow except for white basal ring, third antennal segment black with white ring both basally and apically, apical ring sometimes absent, last segment unicolorous black. Pronotum pale brown, pronotal collar red maculated, posterior margin with narrow white marginal band and wavy and uninterrupted brown submarginal band. Scutellum unicolorous yellowish brown. Hemelytra yellowish brown with scattered reddish pattern, outer margin of corium with red dots interrupted by white coloration along its whole length, very tip of clavus darkened. Outer and inner margins of cuneus with reddish dots interrupted by white coloration, upper inner corner of cuneus with isolated prominent red dot. Membrane brownish with dense pale maculation. Femora reddish brown with numerous white dots of different sizes, tibiae white with broad reddish ring basally and small and irregular reddish spots towards apex, tarsi and claws pale.</p> <p> <i>Vestiture.</i> Upper surface with mostly suberect and rarely erect thick brown setae and adpressed silvery scale-like setae. First antennal segment with several long erect black spines in addition to adpressed brown setae, rest of antennal segments covered only with dense adpressed hyaline setae. Tibial spines pale, femora with long adpressed black setae, vestiture of tibiae as in last three antennal segments.</p> <p> <i>Structure.</i> Body 4.00‒ 4.60 mm long, macropterous, elongate, parallel-sided, 3.5 times as long as basal width of pronotum, head transverse in dorsal view, twice as wide as long, 0.7 times as wide as posterior margin of pronotum and 1.7 times as wide as anterior margin of pronotum, in lateral view as high as long with shallow notch between frons and base of tylus, eyes very large, ocular index 0.6‒0.8. Antennae as long as total length of body. First antennal segment 0.8 times as long as diatone, second antennal segment 1.3 time as long as basal width of pronotum. Ratio of antennal segments 12:30:21:12. Pronotum strongly trapezoid, posterior margin 2.4 times as wide as anterior margin, lateral margins straight. Rostrum reaching posterior coxae.</p> <p>Vesica (Figs 2C‒D) with stick-like long and thick sclerotized process bending slightly in apical third (Fig. 4A), primary membranous sac with weakly sclerotized wrinkles and marginally dentate lamellae (Fig. 2D), several strongly sclerotized structures present near secondary gonopore. Left paramere (Fig. 2E) with sensory lobe slightly produced, hypophysis strongly enlarged before apex. Right paramere elongate, with preapical bulge on right side, apex straight (Fig. 2F).</p> <p> <i>Female.</i> Living specimen, see Fig. 5A. Unfortunatelly, this specimen was not available for description.</p> <p> <b>Differential diagnosis.</b> The new species is placed in the subgenus <i>Exophytocoris</i> Wagner, 1961 of the genus <i>Phytocoris</i> Fallén, 1814 because of the combination of the following features: the first antennal segment ornamented, the third antennal segment brownish with a pale basal ring, head in lateral view as long as high with a shallow notch between frons and base of tylus, and left paramere edentate. The subgenus <i>Exophytocoris</i> includes 25 species (KERZHNER & JOSIFOV 1999, PAGOLA- CARTE 2010, CARAPEZZA 2016, PAGOLA- CARTE & RIEGER 2017). Some of these species were subdivided into three groups in relation to the structure of vesica by LINNAVUORI (1994a). This new species can be placed into the group in which the spiculum is formed of several marginally dentate lamellae (the other two groups have blade-like marginally dentate spiculum or trough-shaped spiculum with both margins dentate). This group of species includes <i>P. koronis</i> Linnavuori, 1992, <i>P. pinihalepensis</i> Lindberg, 1948, <i>P. parvuloides</i> Wagner, 1961, <i>P. scituloides</i> Lindberg, 1948, and <i>P. zenobia</i> Linnavuori, 1994 (LINNAVUORI 1994a). The new species differs from all species of this group in the presence of an additional strongly sclerotized basal process. There are two species which have such a sclerotized process though they are not members of this group: <i>Phytocoris</i> (<i>Exophytocoris</i>) <i>parrotiae</i> Putshkov, 1978, a species endemic to Azerbaijan, which only has a single tooth-like sclerotized process in its vesica according to the original description (PUTSHKOV 1978b), and <i>Phytocoris</i> (<i>Exophytocoris</i>) <i>raunolinnavuorii</i> Carapezza, 2016 which has a small sclerotized process in addition to a lobal sclerite that is unique to this species (CARAPEZZA 2016). <i>Phytocoris carapezzai</i> sp. nov. can be distinguished from <i>P. raunolinnavuorii</i> by much longer sclerotized basal process, presence of dentate lamellae apically, a different left paramere, and dissimilar coloration and patterns of dorsum. <i>Phytocoris carapezzai</i> sp. nov. can also be distinguished from <i>P. parrotiae</i> by different shape of the sclerotized process of vesica which is short, sharp and tooth-like in <i>P. parrotiae</i> and long, thick and stick-like in the new species, by the presence of additional sclerotized structures near secondary gonopore, different shape of the left paramere, and by some other morphological characters such as ocular index, length of the first antennal segment, coloration patterns of pronotum and hemelytra. With respect to its general appearance, the new species might be confused with <i>P. pinihalepensis</i> and <i>P. minor</i> but it can be easily distinguished from them by the dissimilar sclerotized basal process of vesica which is formed of about 10 weakly scletorized marginally dentate lamellae in the former and is comb-like and marginally dentate in the latter but edentate and stick-like in <i>P. carapezzai</i> sp. nov. The new species is also distinguished from many species of the subgenus <i>Exophytocoris</i> by the very small ocular index of male which is 0.6‒0.8, although there are at least two more species, <i>P. pinihalepensis</i> and <i>P. parvuloides</i>, in which the ocular index of male is smaller than 1.0 (WAGNER 1974).</p> <p> <b>Etymology.</b> The name of this new species is dedicated to Attilio Carapezza who is an outstanding specialist and has published lots of precious scientific data on the Heteroptera of the Mediterranean and the Near East. The first author is very grateful to him for his endless help in his first years of work on Heteroptera.</p> <p> <b>Habitat.</b> The UV-light trap that attracted this new species was located in a urban area. There were <i>Populus</i> sp. (Salicaceae), <i>Rosa</i> sp. (Rosaceae), <i>Malus</i> sp. (Rosaceae), <i>Thuja</i> sp. (Cupressaceae), <i>Cedrus</i> sp. (Pinaceae), <i>Juniperus</i> sp. (Cupressaceae), <i>Aesculus</i> sp. (Sapindaceae) trees in the area.</p>Published as part of <i>Çerçi, Barış, Koçak, Özgür & Tezcan, Serdar, 2019, Two new species and ten new records of Heteroptera from Turkey, including the first record of the potential alien Campylomma miyamotoi in the Western Palaearctic, pp. 295-306 in Acta Entomologica Musei Nationalis Pragae 59 (1)</i> on pages 297-299, DOI: 10.2478/aemnp-2019-0023, <a href="http://zenodo.org/record/4488992">http://zenodo.org/record/4488992</a>
Both alcohol and halogenated solvents soluble soft-metal sensor functional phthalocyanines: synthesis, electrochemistry, spectroelectrochemistry
No full textIn this study, we report a novel both alcohol and haloganated solvent soluble selective ionophore functional ligand and its beta-substituted 2(3),9(10),16(17),23(24)-tetrakis(1-hydroxyhexan-3-ylthio)- phthalocyanines, M{Pc[S-CH(CH(2)CH(2)CH(3))(CH(2)CH(2)OH)](4)}, (Pc: Phthalocyanine) (M = Zn, Cu, Co), where -OH indicates peripheral functionality. Pcs exhibiting both hydrophobic and hydrophilic character were characterized spectroscopically (FT-IR, (1)H and (13)C NMR, MS (MALDI-TOF) and UV-vis), electrochemically and spectroelectrochemically. The complexes were soluble in both polar solvents, such as MeOH and EtOH, and non-polar solvents such as CHCl(3), CH(2)Cl(2), benzene, toluene, and even hexane. Absorption spectral changes of the functional MPcs during addition of Ag(I) and Pd(II) soft-metal ions are evaluated by monomer-oligomer and even polymer formations technique and monitored for in situ monitoring technique in the UV-vis spectroscopy. The binding process results in considerable blue-shift in the absorption spectra of MPcs. According to continuous variation method, the ligand: metal ratio was found ca. 1:1 and 1.5:1 for total concentration of 1.0 x 10(-5) M and 7.5 x 10(-5) M, respectively. Their electrochemical and spectroelectrochemical studies show that the complexes exhibited stable monoanionic M{Pc[S-CH(CH(2)CH(2)CH(3))(CH(2)CH(2)OH)](4)}(1-), dianionic M{Pc[S-CH(CH(2)CH(2)CH(3)) (CH(2)CH(2)OH)](4)}(2-) and monocationic M{Pc[S-CH(CH(2)CH(2)CH(3))(CH(2)CH(2)OH)](4)}(1+) species during reduction and oxidation processes
Total Synthesis of Paracaseolide A
No full textThe total synthesis of paracaseolide A, a valuable cell-cycle progression inhibitor, was accomplished in 8 steps from known compounds, with 6.6% overall yield. The synthetic strategy creates strong potential for diversification.Reprinted (adapted) with permission from Organic Letters, 15(3); Doi: 10.1021/ol303447r. Copyright 2013 American Chemical Society.</p
CARİ AÇIĞIN FİNANSMANI VE DOĞRUDAN YABANCI YATIRIMLAR: BRICS-T ÜLKELERİ İÇİN NEDENSELLİK ANALİZİ
No full textGelismekte olan ulkelerin makroekonomik problemlerinden biri olan cari acik ve finansmani konusu, iktisat literaturunde teorik ve ampirik acidan kendine genis bir arastirma alani olusturmustur. Teorik ve ampirik yaklasimlardan hareketle, sermaye akimlari uzerine konulan kisitlamalarin kismen veya tamamen kaldirilmasiyla, artan dogrudan yabanci yatirimlarin ev sahibi ulkede cari acigin finansmani icin kullanilabilecek bir arac oldugu ifade edilmektedir. Bu calismada, dogrudan yabanci yatirimlar ve ortaya cikardigi dinamik etkilerin cari acigin finansmanda nasil bir etkiye sahip oldugu, ceyreklik veri seti kullanilarak 2005:1-2017:4 doneminde BRICS-T ulkeleri icin panel nedensellik analizi ile test edilmistir. Analiz sonuclarina gore, Cin haricindeki diger ulkelerde dogrudan yabanci yatirimlarin cari acigi etkiledigi, bu etkinin en fazla hissedildigi ulkelerin de sirasiyla Guney Afrika, Brezilya ve Turkiye oldugu ortaya cikmistir. Turkiye gibi gelismekte olan ulkelerde cari acigi azaltmak icin dogrudan yabanci yatirimlari tesvik edici politikalarin uygulamaya gecirilmesi gerekmektedir. http://dx.doi.org/10.17130/ijmeb.201935504
Ethical and Methodological Challenges in Research with Hard-to-Reach Groups: Examples from Research on Family Caregivers for Migrant Older Adults Living with Dementia
No full textTezcan-Guntekin H, Ozer-Erdogdu I, Yilmaz-Aslan Y, Aksakal T, Bird R. Ethical and Methodological Challenges in Research with Hard-to-Reach Groups: Examples from Research on Family Caregivers for Migrant Older Adults Living with Dementia. The Gerontologist. 2021.Family caregivers of migrants with dementia constitute a population group that is hard to reach for research participation due to factors such as shame about the disease and past experiences of discrimination. In this paper, research-ethical challenges associated with participant recruitment and qualitative data collection among relatives of migrants with dementia are discussed. Over a period of 8 years, three studies were conducted to investigate the experiences of family caregivers for persons with dementia of Turkish descent in Germany. Across these studies, a total of 32 family caregivers were interviewed. In this paper, based on the "Principles of Biomedical Ethics" according to Beauchamp and Childress (2009), research-ethical conflicts associated with sampling methods and the presence of third parties during qualitative interviews are discussed. The potential risks emanating from sampling strategies and the presence of third parties during interviews regarding the voluntary nature of study participation are examined. Additionally, this paper formulates recommendations for ensuring truly voluntary participation and protecting both the participants (family caregivers) and third parties (especially relatives with dementia) from harm. These practical recommendations aim to help future researchers to avoid ethical pitfalls and represent a roadmap for making necessary methodological decisions. © The Author(s) 2021. Published by Oxford University Press on behalf of The Gerontological Society of America
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