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[formula: see text] The reaction of secondary and primary alcohols with highly fluorinated 3,4,5-tris(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-heptadecafluorododecan- 1-yloxy)benzoic acid in the presence of Ph3P and DIAD in THF at room temperature (fluorous Mitsunobu) resulted in a simple, chromatography-free isolation protocol with excellent yields (83-96%). 相似文献
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Dr. Renata Kaczmarek Samuel Ward Dipra Debnath Taisiya Jacobs Alexander D. Stark Dariusz Korczyński Prof. Dr. Anil Kumar Prof. Dr. Michael D. Sevilla Dr. Sergey A. Denisov Dr. Viacheslav Shcherbakov Dr. Pascal Pernot Prof. Dr. Mehran Mostafavi Prof. Dr. Roman Dembinski Prof. Dr. Amitava Adhikary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9495-9505
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献
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F. de Oliveira Santos P. Himpe M. Lewitowicz I. Stefan N. Smirnova N. L. Achouri J. C. Angélique C. Angulo L. Axelsson D. Baiborodin F. Becker M. Bellegui E. Berthoumieux B. Blank C. Borcea A. Cassimi J. M. Daugas G. de France F. Dembinski C. E. Demonchy Z. Dlouhy P. Dolégiéviez C. Donzaud G. Georgiev L. Giot S. Grévy D. Guillemaud Mueller V. Lapoux E. Liénard M. J. Lopez Jimenez K. Markenroth I. Matea W. Mittig F. Negoita G. Neyens N. Orr F. Pougheon P. Roussel Chomaz M. G. Saint Laurent F. Sarazin H. Savajols M. Sawicka O. Sorlin M. Stanoiu C. Stodel G. Thiamova D. Verney A. C. C. Villari 《The European Physical Journal A - Hadrons and Nuclei》2005,24(2):237-247
The excitation function for the elastic-scattering reaction p( 18Ne, p) 18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed. 相似文献
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H. P. Dembinski 《Physics of Atomic Nuclei》2019,82(6):644-648
The Muon Puzzle is a long-standing issue in the observation of high-energy cosmic rays. In 2018, eight leading air shower experiments combined their data on muons in high-energy air showers and established the existence of an energy-dependent offset with a significance of 8σ. The muon abundance is an important indicator for the cosmic ray mass. The Muon Puzzle needs to be solved to infer the cosmic-ray mass composition unambiguously. It also presents a unique opportunity to learn more about nonperturbative QCD in hadron—nucleus collisions. We will review the status of the Muon Puzzle and discuss an outlook for the future. 相似文献
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Adam Sniady Dr. Michael D. Sevilla Prof. Srinivasarao Meneni Dr. Tadeusz Lis Prof. Slawomir Szafert Prof. Deepthi Khanduri John M. Finke Prof. Roman Dembinski Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(31):7569-7577
Sonogashira coupling of diacetyl 5‐ethynyl‐2′‐deoxyuridine with diacetyl 5‐iodo‐2′‐deoxyuridine gave the acylated ethynediyl‐linked 2′‐deoxyuridine dimer ( 3 b ; 63 %), which was deprotected with ammonia/methanol to give ethynediyl‐linked 2′‐deoxyuridines ( 3 a ; 79 %). Treatment of 5‐ethynyl‐2′‐deoxyuridine ( 1 a ) with 5‐iodo‐2′‐deoxyuridine gave the furopyrimidine linked to 2′‐deoxyuridine (78 %). Catalytic oxidative coupling of 1 a (O2, CuI, Pd/C, N,N‐dimethylformamide) gave butadiynediyl‐linked 2′‐deoxyuridines ( 4 ; 84 %). Double Sonogashira coupling of 5‐iodo‐2′‐deoxyuridine with 1,4‐diethynylbenzene gave 1,4‐phenylenediethynediyl‐bridged 2′‐deoxyuridines ( 5 ; 83 %). Cu‐catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One‐electron addition to 1 a , 3 a , and 4 gave the anion radical, the EPR spectra of which showed that the unpaired electron is largely localized at C6 of one uracil ring (17 G doublet) at 77 K. The EPR spectra of the one‐electron‐oxidized derivatives of ethynediyl‐ and butadiynediyl‐linked uridines 3 a and 4 at 77 K showed that the unpaired electron is delocalized over both rings. Therefore, structures 3 a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that would separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3 b , the bases were found in the anti position relative to each other across the ethynyl link, and similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside. 相似文献
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Reactions of 5-p-tolylethynyl-2'-deoxyuridine and 3',5'-di-O-acetyl-5-p-tolylethynyl-2'-deoxyuridine with Co2(CO)8 in THF gave 5-p-tolC2[CO2(CO)6]-2'-deoxyuridine and 3',5'-di-O-acetyl-5-p-tolC2[CO2(CO)6]-2'-deoxyuridine (92 and 66%). 相似文献