Browsing by Author "Eskici, M"
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Item Asymmetric synthesis of (S)-dihydrokavain from l-malic acidEskici, M; Karanfil, A; Özer, MS; Kabak, Y; Durucasu, IA practical and efficient asymmetric synthesis of (S)-dihydrokavain from known ethyl (S)-2-hydroxy-4-phenylbutanoate which is, in turn, readily available from l-malic acid as a cheap chiral pool material is described using regioselective ring-opening of the 1,2-cyclic sulfate with lithium-3,3,3-triethoxypropiolate and subsequent HgO/H2SO4-mediated lactonization as the key steps. Its opposite enantiomer (R)-dihydrokavain was also synthesized from d-malic acid using the same sequences of reactions for the purpose of optical purity determination. [GRAPHICS] .Item Stereoselective synthesis of cis-2,6-disubstituted piperidines from 1,2-cyclic sulfamidatesEskici, M; Karanfil, ADiastereoselective synthesis of cis-2,6-disubstituted piperidines from 1,2-cyclic sulfamidates is described. Regioselective ring-opening reactions of 1,2-cyclic sulfamidates derived from L-phenylalanine, alanine, valine, norvaline with the ketal protected acetylide with a phenyl substituent proceed smoothly to form the N-sulfamate intermediates which on acidic hydrolysis give alkynylated amines with the ketal group intact. Hydrogenation of the alkynylated amines, debenzylation, ketal deprotection, subsequent cyclization (of aminoketones) and stereoselective hydrogenation of the cyclic iminium ion intermediates afford the corresponding cis-2,6-disubstituted piperidines in high diastereoselectivity (98%>= d.e.) with good chemical yields (68-86%). The present approach provides a novel route for the stereoselective synthesis of cis-2.6-disubstituted piperidines. (C) 2019 Elsevier Ltd. All rights reserved.Item Synthesis, analysis of spectroscopic and nonlinear optical properties of the novel compound: (S)-N-benzyl-1-phenyl-5-(thiophen-3-yl)-4-pentyn-2-amineKarabacak, M; Karaca, C; Atac, A; Eskici, M; Karanfil, A; Kose, EIn this study, a novel compound (S)-N-benzyl-1-phenyl-5-(thiophen-3-yl)-4-pentyn-2-amine (abbreviated as BPTPA) was synthesized and structurally characterized by FT-IR, NMR and UV spectroscopy. The molecular geometry and vibrational frequencies of BPTPA in the ground state have been calculated by using the density functional method (B3LYP) invoking 6-311++G(d,p) basis set. The geometry of the molecule was fully optimized, vibrational spectra were calculated. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (OPDOS) diagrams analysis were given. The energy and oscillator strength of each excitation were calculated by time-dependent density functional theory (TD-DFT) results complements with the experimental findings. The NMR chemical shifts (H-1 and C-13) were recorded and calculated using the gauge invariant atomic orbital (CIAO) method. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizability and first hyper polarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. Finally, vibrational wavenumbers, absorption wavelengths and chemical shifts were compared with calculated values, and found to be in good agreement with experimental results. (C) 2012 Elsevier B.V. All rights reserved.Item Phenolic profile, enzyme inhibitory and antioxidant activities of two endemic Nepeta species: Nepeta nuda subsp. glandulifera and N. cadmeaSarikurkcu, C; Eskici, M; Karanfil, A; Tepe, BIt is known that the local people commonly use some Nepeta species as diuretic, spasmolytic, bronchodilator and sedative agents. In addition, these species are also used topically due to their antiseptic properties. This study aimed to deal with the in vitro antioxidant and enzyme inhibitory activities of the methanolic extracts of two endemic. Nepeta species (Nepeta nuda L. subsp. glandulifera Hub.-Mor. & Davis and N. cadmea Boiss.) from Turkey. N. nuda subsp. glandulifera was found to contain more phenolics and flavonoids than N. cadmea. N. nuda subsp. glandulifera was also found to have considerable amounts of chlorogenic and ferulic acids (63.52 and 14.65 mg/g extract), and showed higher antioxidant activity in almost all test systems, except metal chelating assay. Meanwhile in beta-carotene bleaching assay, it was found to be as active as BHT and trolox (91.23%). In the enzyme inhibition assay, the extracts showed weak inhibitory activity on AChE, alpha-amylase and a-glucosidase. Inhibitory activity of N. nuda subsp. glandulifera on these enzymes was found to be 1.26 mg GALAEs (galanthamine equivalents)/g extract, 0.36 and 3.67 mmol ACEs (acarbose equivalents)/g extract, respectively. (c) 2018 SAAB. Published by Elsevier B.V. All rights reserved.Item Essential oil composition and antioxidant activity of Thymus longicaulis C. Presl subsp longicaulis var. longicaulisSarikurkcu, C; Ozer, MS; Eskici, M; Tepe, B; Can, S; Mete, EThis study is designed to examine the chemical composition and in vitro antioxidant activity of the hydro-distillated essential oil and various extracts obtained from Thymus longicaulis subsp. longicaulis var. Iongicaulis. GC and GC MS analysis of the essential oil were resulted in determination 22 different compounds, representing 99.61% of total oil. gamma-terpinene, thymol and p-cymene were determined as the major compounds of the oil (27.80, 27.65 and 19.38%. respectively). Antioxidant activities of the samples were determined by four different test systems namely beta-carotene/linoleic acid, DPPH, reducing power and chelating effect. Essential oil showed the highest antioxidant activity in beta-carotene/linoleic acid system among the experiments examined. In the case of other test systems, in general, methanol and water extracts exhibited the strongest activity profiles. Especially, reducing power of water extract was found superior than those of synthetic antioxidants. As well as the antioxidant activities of the extracts, they were evaluated in terms of their total phenolic and flavonoid contents. Hexane and water extracts were found to be rich-in phenolics. However, flavonoids were determined in the highest level in methanol extract. (C) 2010 Elsevier Ltd. All rights reserved.Item Reactivity of cyclic sulfamidates towards lithium acetylides: synthesis of alkynylated aminesEskici, M; Karanfil, A; Özer, MS; Sarikürkcü, CA synthetically useful level of reactivity of cyclic sulfamidates toward acetylides is described. Ring-opening reactions of a structurally diverse set of 1,2- and 1,3-cyclic sulfamidates with a range of lithium acetylides from aliphatic, cyclic, aromatic, heteroaromatic, and functionalized alkynes proceed smoothly in a regioselective manner to give the corresponding N-sulfate intermediates. Hydrolysis of these intermediates under acidic conditions furnishes the alkynylated amines in yields ranging from 29% to 98%. The scope of the acetylenic substitution reaction with the structural variations in both the cyclic sulfamidates and alkynes is briefly examined. (C) 2011 Elsevier Ltd. All rights reserved.Item Synthesis, spectroscopic characterization and quantum chemical computational studies of (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amineKose, E; Atac, A; Karabacak, M; Karaca, C; Eskici, M; Karanfil, AThe synthesis and characterization of a novel compound (S)-N-benzyl-1-phenyl-5-(pyridin-2-yl)-pent-4-yn-2-amine (abbreviated as BPPPYA) was presented in this study. The spectroscopic properties of the compound were investigated by FT-IR. NMR and UV spectroscopy experimentally and theoretically. The molecular geometry and vibrational frequencies of the BPPPYA in the ground state were calculated by using density functional theory (OFT) B3LYP method invoking 6-311++G(d,p) basis set. The geometry of the BPPPYA was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The results of the energy and oscillator strength calculated by time-dependent density functional theory (TD-OFT) and CIS approach complement with the experimental findings. Total and partial density of state (TDOS and PDOS) and also overlap population density of state (COOP or OPDOS) diagrams analysis were presented. The theoretical NMR chemical shifts (H-1 and C-13) complement with experimentally measured ones. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The calculated vibrational wavenumbers, absorption wavelengths and chemical shifts showed the best agreement with the experimental results. (C) 2012 Elsevier B.V. All rights reserved.Item A [3+3] cyclization strategy for asymmetric synthesis of alkyl substituted piperidine-2-ones using 1,2-cyclic sulfamidates: a formal synthesis of (S)-coniine from L-norvalineKaranfil, A; Balta, B; Eskici, MRegioselective ring-opening reactions of a set of representative 1,2-cyclic sulfamidates with lithium triethylorthopropiolate proceeded efficiently to deliver the corresponding delta-amino-alpha,beta-unsaturated esters after acidic hydrolysis. Hydrogenation of the unsaturated esters and subsequent thermal cyclization afforded the related alkyl substituted piperidine-2-ones. This approach represents a novel [3+3] cyclization strategy for the asymmetric synthesis of alkyl substituted piperidin-2-ones. Efficiency of the cyclization process is illustrated by a formal asymmetric synthesis of (S)-coniine from L-norvaline. (c) 2012 Elsevier Ltd. All rights reserved.Item Study on lubricant quality and its effect on engine component performanceBesergil, B; Özer, MS; Eskici, M; Atik, EPurpose - This paper aims to determine the usage time of the test lubricant NO, prepared from base oils of Aliaga Plant, Izmir, in gasoline and diesel-engines, and the investigations of high-temperature oxidation, engine-protective properties, and property changes of the lubricant in performance time. Design/methodology/approach - Physical and chemical properties of the lubricating oil were initially established, and the oil was then subjected to Petter W-1 gasoline and Petter AV-1 diesel test engines. Dismantling of the engine parts was followed by the examination of pistons, piston rings and bearings, and analysis of the lubricant was also undertaken. The engine performance test results and the quality control of the lubricating oil assessments were evaluated according to the International Engine Lubricant Specifications. Findings - The lubricating oil, under sluggish experimental conditions, appears to meet a 40-hour test in gasoline engines and a 120-hour test in diesel engines with the specifications. This means that under usual working conditions the lubricants keep the engine protective properties in 7,000 km distance for gasoline run-vehicles, and in 5,000 km distance for diesel run-vehicles, after which change of the oil is required. Originality/value - The paper provides information of value to those involved with lubrication and engine performance.Item Molecular structure, spectroscopic characterization (FT-IR, FT-Raman, UV and NMR), HOMO and LUMO analysis of 3-ethynylthiophene with DFT quantum chemical calculationsKarabacak, M; Bilgili, S; Mavis, T; Eskici, M; Atac, AIn this work, FT-IR, FT-Raman, UV and NMR spectra of 3-ethynylthiophene (3-ETP, C6H4S) were carried out by using density functional theory DFT/B3LYP method with the 6-311++G(d,p), 6-311+G(d,p), 6-311G(d,p), 6-31++G(d,p), 6-31+G(d,p), 6-31G(d,p) basis sets. FT-IR and FT-Raman spectra were recorded in the regions of 3500-400 cm(-1) and 3500-50 cm(-1), respectively. The geometrical parameters, energies and wavenumbers were obtained and the complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method and PQS program. The H-1, C-13 and HMQC (H-1-C-13 correlation) NMR spectra in chloroform (CDCl3) were recorded and calculated. The UV spectrum of investigated compound were recorded in the region of 200-400 nm in ethanol solution. The electronic properties, such as excitation energies, absorption wavelengths, HOMO and LUMO energies were performed by DFT/B3LYP approach and the results were compared with experimental observations. The thermodynamic properties such zero-point vibrational energy, thermal energy, specific heat capacity, rotational constants, entropy, and dipole moment of the studied compound were calculated. As a result, the calculated results were compared with the observed data and found to be in good agreement. (C) 2013 Elsevier B.V. All rights reserved.Item GC/MS Evaluation and In Vitro Antioxidant Activity of Essential Oil and Solvent Extracts of an Endemic Plant Used as Folk Remedy in Turkey: Phlomis bourgaei Boiss.Sarikurkcu, C; Ozer, MS; Cakir, A; Eskici, M; Mete, EThis study was outlined to examine the chemical composition of hydrodistilled essential oil and in vitro antioxidant potentials of the essential oil and different solvent extracts of endemic Phlomis bourgaei Boiss. used as folk remedy in Turkey. The chemical composition of the oil was analyzed by GC and GC-MS, and the predominant components in the oil were found to be beta-caryophyllene (37.37%), (Z)-beta-farnesene (15.88%), and germacrene D (10.97%). Antioxidant potentials of the solvent extracts and the oil were determined by four testing systems including. beta-carotene/linoleic acid, DPPH, reducing power, and chelating effect. In. beta-carotene/linoleic acid assay, all extracts showed the inhibition of more than 50% at all concentrations. In DPPH, chelating effect, and reducing power test systems, the water extract with 88.68%, 77.45%, and 1.857 (absorbance at 700 nm), respectively, exhibited more excellent activity potential than other extracts (hexane, ethyl acetate and methanol) and the essential oil at 1.0 mg/mL concentration. The amount of the total phenolics and flavonoids was the highest in this extract (139.50 +/- 3.98. mu g gallic acid equivalents (GAEs)/mg extract and 22.71 +/- 0.05 mu g quercetin equivalents (QEs)/mg extract).Item Practical synthesis of functionalized terminal alkynes, 3,3,3-triethoxypropyne and ketal protected prop-2-ynonesKaranfil, A; Eskici, MPractical and economical synthesis of synthetically valuable 3,3,3-triethoxypropyne, ketal protected phenyl and methyl substituents prop-2-ynones is described. Bromination and subsequent 18-crown-6 catalyzed elimination of triethylorthoacrylate and ketal protected terminal alkenes with methyl and phenyl substituent which are inturn readily available from triethylorthopropionate, 3-chlorobutan-2-one and propiophenone afforded multigram quantities (>10g) of corresponding functionalized terminal alkynes. Exploration of the synthetic utility of these alkynes is also demonstrated by the acetylenic substitution of the phenylalaninol derived 1,2-cyclic sulfamidate to deliver chiral alkynylated amines. [GRAPHICS] .