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1.
Swinhoeisterol A is a novel steroid with unusual 6/6/5/7 tetracyclic skeleton. The model compound with BCD rings is constructed by Friedel–Crafts acylation and an oxidative dearomatization as key steps. 相似文献
2.
Numerical Algorithms - The LP-Newton method solves linear programming (LP) problems by repeatedly projecting a current point onto a certain relevant polytope. In this paper, we extend the... 相似文献
3.
Front Cover: Construction of a Triangle‐Shaped Trimer and a Tetrahedron Using an α‐Helix‐Inserted Circular Permutant of Cytochrome c555 (Chem. Asian J. 10/2018) 下载免费PDF全文
4.
Shota Ooi Takayuki Tanaka Kyu Hyung Park Dongho Kim Atsuhiro Osuka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(22):6645-6649
The oxidation of 10–10′ singly linked corrole dimers with DDQ at low concentration in CHCl3 afforded meso–meso, β–β, β–β triply linked 2H‐corrole dimers (with two inner NH groups in each corrole unit), which exhibited characteristic 1H NMR and absorption spectra attributable to their nonaromatic electronic networks. These 2H‐corrole dimers were reduced with NaBH4 to aromatic 3H‐corrole dimers, which were unstable and easily oxidized back to the 2H‐corrole dimers upon exposure to air. Bis(zinc(II)) complexes of the 2H‐corrole dimers were synthesized and characterized as rare examples of nonaromatic zinc(II) corrole complexes. 相似文献
5.
Total Synthesis and Structure Elucidation of JBIR‐39: A Linear Hexapeptide Possessing Piperazic Acid and γ‐Hydroxypiperazic Acid Residues 下载免费PDF全文
Dr. Masahito Yoshida Naoki Sekioka Dr. Miho Izumikawa Dr. Ikuko Kozone Dr. Motoki Takagi Dr. Kazuo Shin‐ya Prof. Dr. Takayuki Doi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):3031-3041
The total synthesis and stereochemical structural elucidation of JBIR‐39, containing four nonproteinogenic piperazic acid (Piz) residues, is reported. The synthesis includes Sc(OTf)3‐catalyzed acylation of a Piz(γ‐OTBS) derivative with piperazic acid chloride, providing the desired Piz‐Piz(γ‐OTBS) dipeptide in high yield without epimerization. After assembling two additional Piz moieties and (S)‐isoleucic acid at the N‐terminus, amidation with the (R)‐α‐methylserine ester at the C‐terminus, and deprotection afforded the desired (2R,8S)‐hexapeptide, which is the assumed structure of JBIR‐39. Although the spectral data of the (2R,8S)‐hexapeptide was not identical to JBIR‐39, further synthesis of three stereoisomers confirmed the stereochemical structure of JBIR‐39 to be (2S,6S,8S,11R,16S,21R,26S,27S). 相似文献
6.
Ao‐kai Zhang Jun Ling Kewen Li Guo‐dong Fu Tasuku Nakajima Takayuki Nonoyama Takayuki Kurokawa Jian Ping Gong 《Journal of Polymer Science.Polymer Physics》2016,54(13):1227-1236
In this study, controlled amount of dangling ends is introduced to the two series of poly(ethylene glycol)‐based hydrogel networks with three and four crosslinking functionality by using click chemistry. The structure of the gels with regulated defect percentage is confirmed by comparing the results of low‐field NMR characterization and Monte Carlo simulation. The mechanical properties of these gels were characterized by tensile stress–strain behaviors of the gels, and the results are analyzed by Gent model and Mooney–Rivlin model. The shear modulus of the swollen gels is found to be dependent on the functionality of the network, and decreases with the defect percentage. Furthermore, the value of shear modulus well obeys the Phantom model for all the gels with varied percentage of the defects. The maximum extension ratio, obtained from the fitting of Gent model, is also found to be dependent on the functionality of the network, and does not change with the defect percentage, except at very high defect percentage. The value of the maximum extension ratio is between that predicted from Phantom model and the Affine model. This indicates that at the large deformation, the fluctuation of the crosslinking points is suppressed for some extend but still exists. Polymer volume fractions at various defect percentages obtained from prediction of Flory–Rehner model are found to be in well agreement with the swelling experiment. All these results indicate that click chemistry is a powerful method to regulate the network structure and mechanical properties of the gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1227–1236 相似文献
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Prof. Dr. Azusa Kondoh Takayuki Hirozane Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(42):e202201240
The formal enantioselective umpolung addition of dialkyl phosphites to 2-azaaryl ketones was developed under Brønsted base catalysis. The reaction involves the enantioselective protonation of the transient α-oxygenated (2-azaaryl)methyl anion generated through the 1,2-addition of the anion of dialkyl phosphite to the 2-azaaryl ketone and the subsequent [1,2]-phospha-Brook rearrangement. A chiral bis(guanidino)iminophosphorane organosuperbase efficiently catalyzed the reaction to provide enantio-enriched phosphates in high yields with good to high enantioselectivities. This is a rare example of the catalytic enantioselective protonation of transient carbanions other than enolates, constructing a trisubstituted stereogenic center α to 2-azaarenes. 相似文献
9.
Prof. Dr. Tomoaki Tanase Dr. Kanako Nakamae Yume Okawa Mami Hamada Dr. Arimasa Matsumoto Prof. Dr. Takayuki Nakajima Prof. Dr. Takuya Nakashima Prof. Dr. Tsuyoshi Kawai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(8):e202104060
A P-stereogenic linear tetraphosphine tetraoxide, (R,R)- or (S,S)-dpmppm(=O)4, was synthesized to prepare C2 dinuclear M(hfa)3 complexes (M=Eu, Tb, Y) as the first example of lanthanide(III) complexes with P-chiral multidentate phosphine oxides. The mononuclear M(hfa)3 complexes (M=Eu, Y) with a P-chiral diphosphine dioxide, tpdpb(=O)2, were also prepared, and comparison of their photophysical properties for the EuIII complexes revealed that significant chiral induction from the P-chiral centers arises on the achiral M(hfa)3 units through intramolecular π-π stacking constraint in the dinuclear system. 相似文献
10.
Dr. Tetsuo Tsuchiya Dr. Tomohiko Nakajima Yuko Uzawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9261-9276
This review summarizes the use of photoreactions that replace conventional heating processes for growing oxide thin films from chemical solutions. In particular, this review outlines key variables in photoreactions that affect epitaxial and polycrystalline thin film growth, including precursor materials, laser wavelength, laser fluence, and carbon. In addition, the features of the photoreaction process that can be controlled at a low temperature by oxygen non-stoichiometry are examined. Likewise, functions that are neither achieved by developing a gradient structure nor controlled by a thermal equilibrium reaction are detailed. Two new concepts are presented, known as photoreaction of nanoparticles (PRNP) and photoreaction of a hybrid solutions (PRHS), in which crystal nuclei are pre-dispersed in a metal–organic compound film. This method has successfully produced flexible phosphor films used as resistor or thermistor electronic components. Finally, thin film growth using different light sources such as flash lamps and femtosecond lasers (fs) is explored. 相似文献