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Featured researches published by Asu Usta.


Journal of Asian Natural Products Research | 2005

Triterpenes from Campanula lactiflora

Nuri Yildirim; N. Doğan; Asu Usta; L. Altun

One new triterpene compound, 3β-acetoxylup-20(30)-en-29-al (1) and two known 3-acetylptiloepoxide (2) and 3β-acetoxylup-20(29)-ene (3) were isolated for the first time from the leaves of Campanula lactiflora and their structures were deduced by high field 1D and 2D 400 MHz NMR, EI-MS and (+) LC-MS/MS spectra.


Journal of Molecular Modeling | 2010

Photodimerizations of hydroxy- and benzoylated 4-azachalcones and quantum chemical investigation of the reactions

Ahmet Yaşar; Nuran Yaylı; Asu Usta

Photodimerization reactions of compounds 4–6 gave four new cyclobutane-containing compounds (7–9) with full control over the stereochemistry at the four stereogenic centers. These new cyclobutane-containing compounds had β-truxinic (7a), δ-truxinic (7b and 9), and ε-truxillic (8) structures. However, o-, m-, and p-hydroxy 4-azachalcones (1–3) did not give photochemical cyclization products under any conditions (in solvent or in their solid or molten states). Experimental data suggested the possibility of frontier orbital control over stereochemical behavior, so some theoretical calculations were performed. Full geometrical optimization of compounds 1–9 was performed via DFT B3LYP/6-31+G**, and their electronic structures were also investigated. The geometries of the singlet and triplet states were initially optimized by density functional theory (DFT) and the configuration interaction singles (CIS) B3LYP/3-21+G** level. An additional calculation was performed for the triplet state using the ground-state geometry. The possible photochemical dimerization products of compounds 7–9 (a–g) and the intrinsic reaction coordinates (IRCs) of the reactions of compounds 4–6 were calculated theoretically by the DFT/3-21+G** method. The configurations (reactant, transition state, product, and reaction pathway) corresponding to the stationary points (minima or saddle points) were determined. The intrinsic reaction coordinates were followed to verify the energy profiles that connect each TS to the appropriate local minimum. The dimeric products expected from the calculations coincided with the dimers produced experimentally.


Phytochemistry | 2005

Composition and antimicrobial activity of essential oils from Centaurea sessilis and Centaurea armena

Ahmet Yaşar; Canan Güleç; Asu Usta; Sevgi Kolayli; Kamil Coşkunçelebi; Şengül Alpay Karaoğlu


Turkish Journal of Chemistry | 2003

Chemical Constituents of Campanula lactiflora

Nuri Yildirim; Asu Usta


Helvetica Chimica Acta | 2007

Synthesis, Configuration, and Antimicrobial Properties of Novel Substituted and Cyclized ‘2′,3″-Thiazachalcones’

Asu Usta; Ahmet Yaşar; Nagihan Yılmaz; Canan Güleç; Nuran Yaylı; Şengül Alpay Karaoğlu


Asian Journal of Chemistry | 2009

Chemical composition of the essential oils from flowers of Senecio vernalis and Senecio platyphyllus var. platyphyllus.

Asu Usta; O. Üçüncü; Tayyibe Beyza Cansu; Salih Terzioğlu


Journal of Applied Polymer Science | 2006

Synthesis of novel macromonomeric peroxy initiators of styrene with the cationic copolymerization and the quantum chemically investigation of the initiation system effects

Dilek Kul; Sevil Savaskan Yilmaz; Temel Öztürk; Asu Usta; Murat Misir


Asian Journal of Chemistry | 2010

Volatile constituents and antimicrobial activities from flower and fruit of Arbutus unedo L.

Nuran Kahriman; Canan Albay; N. Doğan; Asu Usta; Sengul Alpay Karaoglu


Turkish Journal of Chemistry | 2009

Synthesis of methyl (E)-2',4''-thiazachalcones and their N-alkyl derivatives, photochemistry with theoretical calculations and antimicrobial activities

Asu Usta; Ahmet Yaşar; Nuran Yaylı; Şengül Alpay Karaoğlu


Turkish Journal of Chemistry | 2006

Cyclic Triterpenoid Saponins from Campanula lactiflora

Asu Usta; Ahmet Yaşar; Osman Üçüncü; Canan Güleç; Mustafa Küçükislamoğlu

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Ahmet Yaşar

Karadeniz Technical University

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Canan Güleç

Karadeniz Technical University

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Nuran Yaylı

Karadeniz Technical University

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Dilek Kul

Karadeniz Technical University

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Murat Misir

Karadeniz Technical University

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N. Doğan

Karadeniz Technical University

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Nuri Yildirim

Karadeniz Technical University

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Sevil Savaskan Yilmaz

Karadeniz Technical University

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Temel Öztürk

Karadeniz Technical University

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