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91.
Dr. Jacorien Coetzee Dr. Deborah L. Dodds Prof. Jürgen Klankermayer Sandra Brosinski Prof. Walter Leitner Prof. Alexandra M. Z. Slawin Prof. David J. Cole‐Hamilton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):11039-11050
Hydrogenation of amides in the presence of [Ru(acac)3] (acacH=2,4‐pentanedione), triphos [1,1,1‐tris‐ (diphenylphosphinomethyl)ethane] and methanesulfonic acid (MSA) produces secondary and tertiary amines with selectivities as high as 93 % provided that there is at least one aromatic ring on N. The system is also active for the synthesis of primary amines. In an attempt to probe the role of MSA and the mechanism of the reaction, a range of methanesulfonato complexes has been prepared from [Ru(acac)3], triphos and MSA, or from reactions of [RuX(OAc)(triphos)] (X=H or OAc) or [RuH2(CO)(triphos)] with MSA. Crystallographically characterised complexes include: [Ru(OAc‐κ1O)2(H2O)(triphos)], [Ru(OAc‐κ2O,O′)(CH3SO3‐κ1O)(triphos)], [Ru(CH3SO3‐κ1O)2(H2O)(triphos)] and [Ru2(μ‐CH3SO3)3(triphos)2][CH3SO3], whereas other complexes, such as [Ru(OAc‐κ1O)(OAc‐κ2O,O′)(triphos)], [Ru(CH3SO3‐κ1O)(CH3SO3‐κ2O,O′)(triphos)], H[Ru(CH3SO3‐κ1O)3(triphos)], [RuH(CH3SO3‐κ1O)(CO)(triphos)] and [RuH(CH3SO3‐κ2O,O′)(triphos)] have been characterised spectroscopically. The interactions between these various complexes and their relevance to the catalytic reactions are discussed. 相似文献
92.
We report a mild and efficient method for introducing deuterium into a range of heterocycles by reacting readily available halide analogues in a deuterodehalogenation reaction using D8-IPA or Et3SiD under palladium-catalysed conditions. 相似文献
93.
Dr. Zijie Zhang Dr. Jiuxing Li Jimmy Gu Ryan Amini Hannah D. Stacey Jann C. Ang Dawn White Prof. Dr. Carlos D. M. Filipe Prof. Dr. Karen Mossman Prof. Dr. Matthew S. Miller Prof. Dr. Bruno J. Salena Prof. Dr. Deborah Yamamura Dr. Payel Sen Prof. Dr. Leyla Soleymani Prof. Dr. John D. Brennan Prof. Dr. Yingfu Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(15):e202200078
We report on a unique DNA aptamer, denoted MSA52, that displays universally high affinity for the spike proteins of wildtype SARS-CoV-2 as well as the Alpha, Beta, Gamma, Epsilon, Kappa, Delta and Omicron variants. Using an aptamer pool produced from round 13 of selection against the S1 domain of the wildtype spike protein, we carried out one-round SELEX experiments using five different trimeric spike proteins from variants, followed by high-throughput sequencing and sequence alignment analysis of aptamers that formed complexes with all proteins. A previously unidentified aptamer, MSA52, showed Kd values ranging from 2 to 10 nM for all variant spike proteins, and also bound similarly to variants not present in the reselection experiments. This aptamer also recognized pseudotyped lentiviruses (PL) expressing eight different spike proteins of SARS-CoV-2 with Kd values between 20 and 50 pM, and was integrated into a simple colorimetric assay for detection of multiple PL variants. This discovery provides evidence that aptamers can be generated with high affinity to multiple variants of a single protein, including emerging variants, making it well-suited for molecular recognition of rapidly evolving targets such as those found in SARS-CoV-2. 相似文献
94.
Shiga Tânia M. Yang Haibing Penning Bryan W. Olek Anna T. McCann Maureen C. Carpita Nicholas C. 《Cellulose (London, England)》2021,28(9):5305-5319
Cellulose - A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD4 to 6-deutero- and... 相似文献
95.
Dr. Koushik Chandra Dr. Tapta Kanchan Roy Dr. Deborah E. Shalev Prof. Abraham Loyter Prof. Chaim Gilon Prof. R. Benny Gerber Prof. Assaf Friedler 《Angewandte Chemie (International ed. in English)》2014,53(36):9450-9455
We present a new approach for peptide cyclization during solid phase synthesis under highly acidic conditions. Our approach involves simultaneous in situ deprotection, cyclization and trifluoroacetic acid (TFA) cleavage of the peptide, which is achieved by forming an amide bond between a lysine side chain and a succinic acid linker at the peptide N‐terminus. The reaction proceeds via a highly active succinimide intermediate, which was isolated and characterized. The structure of a model cyclic peptide was solved by NMR spectroscopy. Theoretical calculations support the proposed mechanism of cyclization. Our new methodology is applicable for the formation of macrocycles in solid‐phase synthesis of peptides and organic molecules. 相似文献
96.
Evan S. O'Brien Brian Fuglestad Henry J. Lessen Matthew A. Stetz Danny W. Lin Bryan S. Marques Kushol Gupta Karen G. Fleming A. Joshua Wand 《Angewandte Chemie (International ed. in English)》2020,59(27):11108-11114
The internal motions of integral membrane proteins have largely eluded comprehensive experimental characterization. Here the fast side‐chain dynamics of the α‐helical sensory rhodopsin II and the β‐barrel outer membrane protein W have been investigated in lipid bilayers and detergent micelles by solution NMR relaxation techniques. Despite their differing topologies, both proteins have a similar distribution of methyl‐bearing side‐chain motion that is largely independent of membrane mimetic. The methyl‐bearing side chains of both proteins are, on average, more dynamic in the ps–ns timescale than any soluble protein characterized to date. Accordingly, both proteins retain an extraordinary residual conformational entropy in the folded state, which provides a counterbalance to the absence of the hydrophobic effect. Furthermore, the high conformational entropy could greatly influence the thermodynamics underlying membrane‐protein functions, including ligand binding, allostery, and signaling. 相似文献
97.
Nika Mahne Sara E. Renfrew Prof. Bryan D. McCloskey Dr. Stefan A. Freunberger 《Angewandte Chemie (International ed. in English)》2018,57(19):5529-5533
Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal‐O2 batteries, and are believed to form and decompose reversibly in metal‐O2/CO2 cells. In these cathodes, Li2CO3 decomposes to CO2 when exposed to potentials above 3.8 V vs. Li/Li+. However, O2 evolution, as would be expected according to the decomposition reaction 2 Li2CO3→4 Li++4 e?+2 CO2+O2, is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1O2) forms upon oxidizing Li2CO3 in an aprotic electrolyte and therefore does not evolve as O2. These results have substantial implications for the long‐term cyclability of batteries: they underpin the importance of avoiding 1O2 in metal‐O2 batteries, question the possibility of a reversible metal‐O2/CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition‐metal cathodes with residual Li2CO3. 相似文献
98.
A Scalable Biomimetic Synthesis of Resveratrol Dimers and Systematic Evaluation of their Antioxidant Activities 下载免费PDF全文
Bryan S. Matsuura Mitchell H. Keylor Bo Li YuXuan Lin Shelby Allison Prof. Dr. Derek A. Pratt Prof. Dr. Corey R. J. Stephenson 《Angewandte Chemie (International ed. in English)》2015,54(12):3754-3757
An efficient synthetic route to the resveratrol oligomers quadrangularin A and pallidol is reported. It features a scalable biomimetic oxidative dimerization that proceeds in excellent yield and with complete regioselectivity. A systematic evaluation of the natural products and their synthetic precursors as radical‐trapping antioxidants has revealed that, contrary to popular belief, this mode of action is unlikely to account for their observed biological activity. 相似文献
99.
Nicholas J. Youngman Matthew R. Lewin Rebecca Carter Arno Naude Bryan G. Fry 《Molecules (Basel, Switzerland)》2022,27(5)
Snakebite remains a significant public health burden globally, disproportionately affecting low-income and impoverished regions of the world. Recently, researchers have begun to focus on the use of small-molecule inhibitors as potential candidates for the neutralisation of key snake venom toxins and as potential field therapies. Bitis vipers represent some of the most medically important as well as frequently encountered snake species in Africa, with a number of species possessing anticoagulant phospholipase A2 (PLA2) toxins that prevent the prothrombinase complex from inducing clot formation. Additionally, species within the genus are known to exert pseudo-procoagulant activity, whereby kallikrein enzymatic toxins cleave fibrinogen to form a weak fibrin clot that rapidly degrades, thereby depleting fibrinogen levels and contributing to the net anticoagulant state. Utilising well-validated coagulation assays measuring time until clot formation, this study addresses the in vitro efficacy of three small molecule enzyme inhibitors (marimastat, prinomastat and varespladib) in neutralising these aforementioned activities. The PLA2 inhibitor varespladib showed the greatest efficacy for the neutralisation of PLA2-driven anticoagulant venom activity, with the metalloproteinase inhibitors prinomastat and marimastat both showing low and highly variable degrees of cross-neutralisation with PLA2 anticoagulant toxicity. However, none of the inhibitors showed efficacy in neutralising the pseudo-procoagulant venom activity exerted by the venom of B. caudalis. Our results highlight the complex nature of snake venoms, for which single-compound treatments will not be universally effective, but combinations might prove highly effective. Despite the limitations of these inhibitors with regards to in vitro kallikrein enzyme pseudo-procoagulant venom activity, our results further support the growing body of literature indicating the potential use of small molecule inhibitors to enhance first-aid treatment of snakebite envenoming, particularly in cases where hospital and thus antivenom treatment is either unavailable or far away. 相似文献
100.