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421.
Keisuke Sakurai Prof. Dr. Makoto Sasaki Prof. Dr. Haruhiko Fuwa 《Angewandte Chemie (International ed. in English)》2018,57(18):5143-5146
Total synthesis of (?)‐enigmazole A, a marine macrolide natural product with cytotoxic activity, has been accomplished. The tetrahydropyran moiety was constructed by means of a domino olefin cross‐metathesis/intramolecular oxa‐Michael addition of a δ‐hydroxy olefin. After coupling of advanced intermediates, the macrocycle was formed through gold‐catalyzed rearrangement of a propargylic benzoate, followed by ring‐closing metathesis of the resultant α,β‐unsaturated ketone. 相似文献
422.
Yongfeng Tao Jan G. Felber Zhongyu Zou Evert Njomen Jarrett R. Remsberg Daisuke Ogasawara Chang Ye Bruno Melillo Stuart L. Schreiber Chuan He David Remillard Benjamin F. Cravatt 《Angewandte Chemie (International ed. in English)》2023,62(51):e202311924
5-Methylcytosine (m5C) is an RNA modification prevalent on tRNAs, where it can protect tRNAs from endonucleolytic cleavage to maintain protein synthesis. The NSUN family (NSUN1-7 in humans) of RNA methyltransferases are capable of installing the methyl group onto the C5 position of cytosines in RNA. NSUNs are implicated in a wide range of (patho)physiological processes, but selective and cell-active inhibitors of these enzymes are lacking. Here, we use cysteine-directed activity-based protein profiling (ABPP) to discover azetidine acrylamides that act as stereoselective covalent inhibitors of human NSUN2. Despite targeting a conserved catalytic cysteine in the NSUN family, the NSUN2 inhibitors show negligible cross-reactivity with other human NSUNs and exhibit good proteome-wide selectivity. We verify that the azetidine acrylamides inhibit the catalytic activity of recombinant NSUN2, but not NSUN6, and demonstrate that these compounds stereoselectively disrupt NSUN2-tRNA interactions in cancer cells, leading to a global reduction in tRNA m5C content. Our findings thus highlight the potential to create isotype-selective and cell-active inhibitors of NSUN2 with covalent chemistry targeting a conserved catalytic cysteine. 相似文献
423.
Inada A Ogasawara R Koga I Nakatani N Inatomi Y Murata H Nishi M Nakanishi T 《Chemical & pharmaceutical bulletin》2008,56(5):727-729
Three novel furoquinoline alkaloid oxogeranyl ethers (1-3) and one known furoquinoline alkaloid (4) were isolated from the leaves of Boninia glabra, an endemic plant of the Bonin Islands. Their structures were elucidated on the basis of spectroscopic analysis. 相似文献
424.
425.
Nordlund D Ogasawara H Bluhm H Takahashi O Odelius M Nagasono M Pettersson LG Nilsson A 《Physical review letters》2007,99(21):217406
We determine electron delocalization rates in liquid water and ice using core-hole decay spectroscopy. The hydrogen-bonded network delocalizes the electrons in less than 500 as. Broken or weak hydrogen bonds--in the liquid or at the surface of ice--provide states where the electron remains localized longer than 20 fs. These asymmetrically bonded water species provide electron traps, acting as a strong precursor channel to the hydrated electron. 相似文献
426.
Strategies have been developed for the synthesis of 2-substituted indoles and indolines starting from acyclic alpha-phosphoryloxy enecarbamates. A highly chemoselective cross-coupling of N-(o-bromophenyl)-alpha-phosphoryloxyenecarbamates with boron nucleophiles enabled the efficient preparation of various N-(o-bromophenyl)enecarbamates, which served as useful precursors for subsequent Heck-type cyclization or 5-endo-trig aryl radical cyclization to furnish 2-substituted indoles or indolines, respectively. 相似文献
427.
An intramolecular Heck/Diels-Alder cycloaddition cascade starting from acyclic alpha-phosphono enecarbamates has been developed to prepare nitrogen heterocycles via indole-2,3-quinodimethanes and 2-(N-alkoxycarbonylamino)-1,3-dienes. 相似文献
428.
Ito H Oda K Kawamura Y Saitoh H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(1):39-47
CN(X(2)Sigma(+)) radicals were produced by the decomposition of BrCN with the microwave discharge flow of Ar under the conditions of Ar pressure in the range of 0.40-0.70 Torr. The laser-induced fluorescence (LIF) spectra of the CN(A(2)Pi(i)-X(2)Sigma(+)), 4-0, 5-1, and 7-2 bands were observed, and their intensities were calibrated against Rayleigh-scattering intensity by Ar atoms, from which the CN(X(2)Sigma(+)) radical density (n(CN(X))) was determined as (0.67+/-0.25) x 10(18) to (4.42+/-0.83) x 10(18) m(-3). Hydrogenated amorphous carbon nitride (a-CN(x):H) films were formed by depositing the CN(X(2)Sigma(+)) radicals on Si substrates in the same reaction system as LIF. The sticking probability (s) of the CN(X(2)Sigma(+)) radicals onto the a-CN(x):H films was determined by using n(CN(X)), the flow speed, and the weight (w) of a-CN(x):H. The s value was determined as (6.4+/-6.4) x 10(-2) to (2.5+/-1.2) x 10(-2), where the errors are predominantly determined by those in n(CN(X)) and w. The procedure described in the present study will provide a methodology to determine the sticking probability of the precursor radicals of the film formation based on the gas-phase LIF spectroscopy. 相似文献
429.
Naofumi Naga Hiroki Sakai Chiharu Usui Haruhiko Tomoda 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3542-3552
Copolymerizations of ethylene or propylene and allyl monomers containing 9‐fluorenyl group, diallyl‐di‐9‐fluorenylsilane (DAFS), 9,9‐diallylfluorene (DAF), and 9‐allylfluorene (AF), were investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged zirconocene catalysts, especially a syndioselective catalyst, showed a higher reactivity for all the comonomers than the nonbridged catalysts. DAFS was mainly incorporated into the polymer chain via cyclization insertion, whereas DAF was copolymerized via both 1,2‐ and cyclization insertions. Cyclization selectivity, ratio of cyclized insertion unit, of DAF in the copolymerization with propylene was higher than that in the copolymerization with ethylene. Copolymerization with AF yielded low‐molecular weight copolymer because of frequent chain transfer reaction. Optical properties of the propylene based‐copolymers were investigated by UV‐vis and photoluminescence spectroscopy, and absorption‐ and emission‐derived from fluorenyl groups were detected in the copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3542–3552, 2010 相似文献
430.