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121.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis 下载免费PDF全文
122.
Beyond Stereoselectivity,Switchable Catalysis: Some of the Last Frontier Challenges in Ring‐Opening Polymerization of Cyclic Esters 下载免费PDF全文
Dr. Sophie M. Guillaume Dr. Evgueni Kirillov Dr. Yann Sarazin Prof. Dr. Jean‐François Carpentier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):7988-8003
Metal‐based catalysts and initiators have played a pivotal role in the ring‐opening polymerization (ROP) of cyclic esters, thanks to their high activity and remarkable ability to control precisely the architectures of the resulting polyesters in terms of molar mass, dispersity, microstructure, or tacticity. Today, after two decades of extensive research, the field is slowly reaching maturity. However, several challenges remain, while original concepts have emerged around new types or new applications of catalysis. This Review is not intended to comprehensively cover all of these aspects. Rather, it provides a personal overview of the very recent progress achieved in some selected, important aspects of ROP catalysis—stereocontrol and switchable catalysis. Hence, the first part addresses the development of new metal‐based catalysts for the isoselective ROP of racemic lactide towards stereoblock copolymers, and the use of syndioselective ROP metal catalysts to control the monomer sequence in copolymers. A second part covers the development of ROP catalysts—primarily metal‐based catalysts, but also organocatalysts—that can be externally regulated by the use of chemical or photo stimuli to switch them between two states with different catalytic abilities. Current challenges and opportunities are highlighted. 相似文献
123.
Caterpillar Track Complexes in Template‐Directed Synthesis and Correlated Molecular Motion 下载免费PDF全文
Shiqi Liu Dr. Dmitry V. Kondratuk Dr. Sophie A. L. Rousseaux Dr. Guzmán Gil‐Ramírez Dr. Melanie C. O'Sullivan Jonathan Cremers Prof. Tim D. W. Claridge Prof. Harry L. Anderson 《Angewandte Chemie (International ed. in English)》2015,54(18):5355-5359
Small alterations to the structure of a star‐shaped template totally change its mode of operation. The hexapyridyl template directs the conversion of a porphyrin dimer to the cyclic hexamer, but deleting one pyridine site changes the product to the cyclic decamer, while deleting two binding sites changes the product to the cyclic octamer. This surprising switch in selectivity is explained by the formation of 2:1 caterpillar track complexes, in which two template wheels bind inside the nanoring. Caterpillar track complexes can also be prepared by binding the hexapyridyl template inside the 8‐ and 10‐porphyrin nanorings. NMR exchange spectroscopy (EXSY) experiments show that these complexes exhibit correlated motion, in which the conrotatory rotation of the two template wheels is coupled to rotation of the nanoring track. In the case of the 10‐porphyrin system, the correlated motion can be locked by binding palladium(II) dichloride between the two templates. 相似文献
124.
Groni S Dorlet P Blain G Bourcier S Guillot R Anxolabéhère-Mallart E 《Inorganic chemistry》2008,47(8):3166-3172
In the present work we report the reactivity of [LMnII]2+ toward addition of hydrogen peroxide (H2O2) in acetonitrile solution, where L is a pentadentate polypyridine ligand. Formation of peroxo complexes is evidenced by low-temperature UV-visible spectroscopy, ESI-mass spectrometry, and EPR spectroscopy using parallel as well as perpendicular mode detection. The influence of the medium (basicity, water content) on the formation of various species is investigated. In basic nonanhydrous medium the fate of the reaction mixture solution is the formation of the di-mu-oxo mixed-valent Mn(III)Mn(IV) dinuclear complex. In acidic medium the building of the oxo bridges is avoided and the reaction mixture evolves toward oxidation of the ligand L. This reaction route offers new opportunities for the study of oxidation reactivity of Mn (hydro)peroxo complexes. 相似文献
125.
Paramagnetic liposomes: inner versus outer membrane relaxivity of DPPC liposomes incorporating lipophilic gadolinium complexes 总被引:1,自引:0,他引:1
Laurent S Elst LV Thirifays C Muller RN 《Langmuir : the ACS journal of surfaces and colloids》2008,24(8):4347-4351
Proton relaxometric properties of unilamellar DPPC liposomes embedding an amphiphilic paramagnetic chelate (Gd-DTPA-BC(14)A) in both layers of the phospholipid membrane or only in the external one are compared. The results show that the membrane's water permeability is able to quench the effect of the paramagnetic complexes located in the internal layer of DPPC liposomes, leading thus to an apparent lower global relaxivity. 相似文献
126.
Caruso A Voisin-Chiret AS Lancelot JC Sinicropi MS Garofalo A Rault S 《Molecules (Basel, Switzerland)》2008,13(6):1312-1320
A synthetic method for the preparation of 6-aryl-1,4-dimethyl-9H-carbazoles involving a palladium catalyzed coupling reaction of 1,4-dimethyl-9H-carbazole-6-boronic acids and (hetero)aryl halides is described. 相似文献
127.
Enantiopure 1,4-difluoro-cyclohexenes were prepared from readily available acetonide-protected (3 S,4 S)-hexa-1,5-diene-3,4-diol. In a two-directional mode, a double cross-metathesis reaction using allyltrimethylsilane as the olefinic partner, followed by electrophilic fluorination, afforded diastereomeric acetonide-protected 3,6-difluoro-octa-1,7-diene-4,5-diols. These dienes were found to be suitable substrates for ring-closing metathesis, delivering cyclohexenes featuring fluorine atoms on the two allylic positions flanking the double bond. Upon dihydroxylation, novel difluorinated cyclitol analogues were formed. 相似文献
128.
Ania Alik Chafiaa Bouguechtouli Manon Julien Wolfgang Bermel Rania Ghouil Sophie Zinn‐Justin Francois‐Xavier Theillet 《Angewandte Chemie (International ed. in English)》2020,59(26):10411-10415
Abundant phosphorylation events control the activity of nuclear proteins involved in gene regulation and DNA repair. These occur mostly on disordered regions of proteins, which often contain multiple phosphosites. Comprehensive and quantitative monitoring of phosphorylation reactions is theoretically achievable at a residue‐specific level using 1H‐15N NMR spectroscopy, but is often limited by low signal‐to‐noise at pH>7 and T>293 K. We have developed an improved 13Cα‐13CO correlation NMR experiment that works equally at any pH or temperature, that is, also under conditions at which kinases are active. This allows us to obtain atomic‐resolution information in physiological conditions down to 25 μm . We demonstrate the potential of this approach by monitoring phosphorylation reactions, in the presence of purified kinases or in cell extracts, on a range of previously problematic targets, namely Mdm2, BRCA2, and Oct4. 相似文献
129.
Hideyuki Tatsuno Kasper S. Kjr Kristjan Kunnus Tobias C. B. Harlang Cornelia Timm Meiyuan Guo Pavel Chbera Lisa A. Fredin Robert W. Hartsock Marco E. Reinhard Sergey Koroidov Lin Li Amy A. Cordones Olga Gordivska Om Prakash Yizhu Liu Mads G. Laursen Elisa Biasin Frederik B. Hansen Peter Vester Morten Christensen Kristoffer Haldrup Zoltn Nmeth Dorottya Srosin Szemes va Bajnczi Gyrgy Vank Tim B. Van Driel Roberto Alonso‐Mori James M. Glownia Silke Nelson Marcin Sikorski Henrik T. Lemke Dimosthenis Sokaras Sophie E. Canton Asmus O. Dohn Klaus B. Mller Martin M. Nielsen Kelly J. Gaffney Kenneth Wrnmark Villy Sundstrm Petter Persson Jens Uhlig 《Angewandte Chemie (International ed. in English)》2020,59(1):364-372
Iron N‐heterocyclic carbene (NHC) complexes have received a great deal of attention recently because of their growing potential as light sensitizers or photocatalysts. We present a sub‐ps X‐ray spectroscopy study of an FeIINHC complex that identifies and quantifies the states involved in the deactivation cascade after light absorption. Excited molecules relax back to the ground state along two pathways: After population of a hot 3MLCT state, from the initially excited 1MLCT state, 30 % of the molecules undergo ultrafast (150 fs) relaxation to the 3MC state, in competition with vibrational relaxation and cooling to the relaxed 3MLCT state. The relaxed 3MLCT state then decays much more slowly (7.6 ps) to the 3MC state. The 3MC state is rapidly (2.2 ps) deactivated to the ground state. The 5MC state is not involved in the deactivation pathway. The ultrafast partial deactivation of the 3MLCT state constitutes a loss channel from the point of view of photochemical efficiency and highlights the necessity to screen transition‐metal complexes for similar ultrafast decays to optimize photochemical performance. 相似文献
130.
Luke Green Keith Livingstone Dr. Sophie Bertrand Dr. Simon Peace Dr. Craig Jamieson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14866-14870
A range of 1,3,4-oxadiazoles have been synthesized using a UV-B activated flow approach starting from carboxylic acids and 5-substituted tetrazoles. The application of UV light represents an attractive alternative to the traditional thermolytic approach and has demonstrated comparable efficiency and versatility, with a diverse substrate scope, including the incorporation of highly substituted amino acids. 相似文献