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1.
Mátyás Milen László Hazai Pál Kolonits György Kalaus Lajos Szabó Ágnes Gömöry Csaba Szántay 《Central European Journal of Chemistry》2005,3(1):118-136
Transformation of β-carboline derivatives into optically active entities were studied and the de and ee values of the resulted compounds were detected.
Dedicated to Professor Károly Lempert on his 80th birthday. 相似文献
2.
Milen Raytchev Elke Mayer Nicole Amann Hans-Achim Wagenknecht Torsten Fiebig 《Chemphyschem》2004,5(5):706-712
5-(Pyren-1-yl)-2'-deoxyuridine (PydU) and 5-(Pyren-1-yl)-2'-deoxycytidine (PydC) were used as model nucleosides for DNA-mediated reductive electron transport (ET) in steady-state fluorescence and femtosecond time-resolved transient absorption spectroscopy studies. Excitation of the pyrene moiety in PydU and PydC leads to an intramolecular electron transfer that yields the pyrenyl radical cation and the corresponding pyrimidine radical anion (dU.- and dC.-. By comparing the excited state dynamics of PydC and PydU, we derived information about the energy difference between the two pyrimidine radical anion states. To determine the influence of protonation on the rates of photoinduced intramolecular ET, the spectroscopic investigations were performed in acetonitrile, MeCN, and in water at different pH values. The results show a significant difference in the basicity of the generated pyrimidine radical anions and imply an involvement of proton transfer during electron hopping in DNA. Our studies revealed that the radical anion dC.- is being protonated even in basic aqueous solution on a picosecond time scale (or faster). These results suggest that protonation of dC.- may also occur in DNA. In contrast, efficient ET in PydU could only be observed at low pH values (< 5). In conclusion, we propose--based on the free energy differences and the different basicities--that only dT.- but not dC.- can participate as an intermediate charge carrier for excess electron migration in DNA. 相似文献
3.
J. Fekete M. Milen L. Hazai L. Poppe Cs. Szántay A. Kettrup I. Gebefügi 《Chromatographia》2003,57(3-4):147-153
Summary Reversed (RP-HPLC) and normal phase chromatographic (NP-HPLC) separations have been developed for diastereomers ofN-acyl-1-methyl-1,2,3,4-tetrahydo-β-carbolines which are acylated derivatives of simple natural β-carboline alkaloids. Separations
of derivatives having different acyl moieties in theO,O-diacyl-tartaric acid ester subtituent differed remarkably. Little or no resolution in either NP-HPLC or RP-HPLC could be
achieved with the diacetyl-tartrate derivative. Base-line separation by RP-HPLC but no separation by NP-HPLC was possible
with the bulkier and more apolar dipivaloyl derivative. Retention order of the bis-benzoylated diastereomers was reversed
and separation time increased dramatically by RP-HPLC. Good separation of the medium polarity, but rigid,N-camphanyl derivative by NP-HPLC has been achieved, whereas RP-HPLC could not be used for separation of these diastereomers.
Separability of different diastereomers was highly dependent on polarity and rigidity of the derivatizingN-acyl moieties. Conformational analysis by molecular mechanics and comparison of the lowest energy conformational states of
the diastereomers was applied to rationalise separation-retention behaviour of stereoisomers by RP-HPLC.
Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001 相似文献
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5.
Journal of Mathematical Chemistry - We mathematically analyze the solutions to the dynamical system induced by the two-step exponential (growth-)decay (2SED) reaction network involving three... 相似文献
6.
We provide a simple proof of the Moreau-Rockafellar theorem that a proper lower semicontinuous convex function on a Banach space is determined up to a constant by its subdifferential.
7.
Tímea Szabó András Dancsó Péter Ábrányi-Balogh Balázs Volk Mátyás Milen 《Tetrahedron letters》2019,60(20):1353-1356
In the present work, a propylphosphonic anhydride (T3P®) assisted Robinson–Gabriel cyclization of N-acyl-β-oxotryptamines for the synthesis of 2-substituted-5-(3-indolyl)oxazoles has been developed. The reactions proceeded smoothly in acetonitrile under microwave irradiation, and the product isolation required only an extraction and subsequent crystallization; no chromatography was necessary. The desired products were obtained in good to excellent yields. 相似文献
8.
Propylphosphonic anhydride (T3P®) was successfully applied to the synthesis of an isoindolinone library by the utilization of an Ugi four-center, three-component reaction (Ugi-4C-3CR). The use of T3P® significantly shortened the required reaction time and the corresponding products were obtained in good to high yields. Moreover, a side-reaction was observed when phenylethylamine derivatives and tryptamine were used as the amine component. The latter reaction was applied to the microwave-assisted, one-pot synthesis of the isoquinoline alkaloid (±)-nuevamine. Surprisingly, the traditional Ugi four-component reaction (Ugi-4CR) was unsuccessful in the presence of T3P®. In this case an α-amino amide was produced excluding the carboxylic acid from the multicomponent reaction. 相似文献
9.
Milen G. Bogdanov Mariana D. Palamareva Blagovesta T. Gocheva Darina B. Dimitrova 《Journal of heterocyclic chemistry》2007,44(3):673-677
10.
The reactions of thiocarbonyl compounds with cis‐2,3‐dimethyloxirane ( 1a ) in CH2Cl2 in the presence of BF3⋅Et2O or SnCl4 led to trans‐4,5‐dimethyl‐1,3‐oxathiolanes, whereas with trans‐2,3‐dimethyloxirane ( 1b ) cis‐4,5‐dimethyl‐1,3‐oxathiolanes were formed. With the stronger Lewis acid SnCl4, the formation of side‐products was also observed. In the case of 1,3‐thiazole‐5(4H)‐thione 2 , these side‐products are the corresponding 1,3‐thiazol‐5(4H)‐one 5 and the 1 : 2 adduct 8 (Schemes 2 – 4). Their formation can be rationalized by the decomposition of the initially formed spirocyclic 1,3‐oxathiolane and by a second addition onto the C=N bond of the 1 : 1 adduct, respectively. The secondary epimerization by inversion of the configuration of the spiro‐C‐atom (Schemes 5 – 7) can be explained by a Lewis‐acid‐catalyzed ring opening of the 1,3‐oxathiolane ring and subsequent ring closure to the thermodynamically more stable isomer (Scheme 12). In the case of 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone ( 20 ), apart from the expected spirocyclic 1,3‐oxathiolanes 21 and 23 , dispirocyclic 1 : 2 adducts were formed by a secondary addition onto the C=O group of the four‐membered ring (Schemes 9 and 10). 相似文献