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81.
[structure: see text] Stereoselective total synthesis of scytophycin C, a marine 22-membered macrolide displaying potent activity against a variety of human carcinoma cell lines, has been reported in which the polypropionate structure bearing contiguous asymmetric centers was stereospecifically constructed by using new acyclic stereocontrol. This paper describes stereoselective syntheses of the C(1)-C(18) segment (Segment A) including a trans-disubstituted dihydropyran ring and the C(19)-C(31) segment (Segment B) having eight stereogenic centers. 相似文献
82.
John Hendri Akihiro Hiroki Hiroyuki Oku Masaru Yoshida Ryoichi Katakai 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):56-62
The volume phase transition of nonionic hydrogels was controlled with a very small amount of variation (pinpoint variation) of the side chains far from the main chain. The copolymer hydrogels poly(methacryloyl‐alanine methyl ester‐co‐methacryloyl‐alanine ethyl ester) [poly(MA‐Ala‐OMe‐co‐MA‐Ala‐OEt)] and poly(methacryloyl‐alanine alkylamide‐co‐methacryloyl‐alanine ethyl ester) [poly(MA‐Ala‐NR2‐co‐MA‐Ala‐OEt)] were studied to investigate how pinpoint variation controls the volume phase transition. All copolymer hydrogels showed a volume phase transition from a swollen phase to a collapsed phase at a definite MA‐Ala‐OEt content at a specific temperature. The MA‐Ala‐OEt content at the midpoint of the transition linearly decreased with elevation of the temperature, and the decrease was larger for poly(MA‐Ala‐OMe‐co‐MA‐Ala‐OEt) than for poly(MA‐Ala‐NR2‐co‐MA‐Ala‐OEt). These results suggest that the association of the side chains controlling the swelling character of the hydrogels depends on the interacting ester–ester or ester–amide groups, and the former is larger than the latter. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 56–62, 2001 相似文献
83.
Kenta Tanaka Ryoichi Akimoto Tetsutaro Igarashi Tadamitsu Sakurai 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):25-31
An investigation was undertaken to shed much light on the bond‐cleavage mode (heterolysis vs homolysis) of bichromophoric photoinitiators in styrene (St) and 1,2‐epoxycyclohexane (EpC) and then to develop a highly efficient hybrid‐type photoinitiator. Excited‐state 2‐(9‐anthrylmethyloxy)‐6‐cyanonaphthalene in toluene and 1,2‐dimethoxyethane, which were used instead of St and EpC, respectively, underwent both homolytic Ar? OCH2 bond cleavage and heterolytic ArO? CH2 bond cleavage to give the corresponding radical‐pair and ion‐pair intermediates. The charge‐separated state characteristic of the naphthol chromophore in the singlet excited state was found to play a pivotal role in this heterolytic bond‐cleavage mode. An inspection of the radical (St) and cationic (EpC) photopolymerization behavior observed in the presence of some 2‐arylmethyloxy‐6‐cyanonaphthalenes led us to conclude that the aforementioned 9‐anthrylmethyloxy‐substituted naphthalene derivative is a candidate for a functional hybrid‐type photoinitiator containing no halogen and/or metal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 25–31, 2006 相似文献
84.
85.
Ryoichi Nakagaki Noriko Kitamura Iwao Aoyama Hiromi Ohtsubo 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):113-119
The absorption and fluorescence spectra of 7-aminocoumarins and 7-aminocarbostyrils with different degrees of alkylation were studied in 2-propanol (IP), polyfluorinated alcohols and water. The spectral properties of substituted 7-aminocoumarins and 7-aminocarbostyrils in hexafluoro-2-propanol (HFP) are very different from those in 2-propanol due to the strong hydrogen-bonding (HB) interaction between the solute and the solvent (HFP). The spectral behaviour can be explained in terms of the strength of the HB interaction which depends on the degree of alkylation of the amino group and the electron affinity of the electron-accepting moiety. The absorption spectra indicate that a structural change at the amino nitrogen is induced on formation of strong hydrogen bonds. 相似文献
86.
We describe herein a stereo-controlled and practical synthesis of three key building blocks, namely Segment AB′, Segment D, and Segment E′ needed for the total synthesis of (−)-kazusamycin A. 相似文献
87.
88.
Ryoichi Shimizu 《Annals of the Institute of Statistical Mathematics》1987,39(1):611-622
Summary LetX be a standard normal random variable and let σ be a positive random variable independent ofX. The distribution of η=σX is expanded around that ofN(0, 1) and its error bounds are obtained. Bounds are given in terms of E(σ
2V−σ
2−1)
k
whereσ
2Vσ
−2 denotes the maximum of the two quantitiesσ
2 andσ
−2, andk is a positive integer, and of E(σ
2−1)
k
, ifk is even.
The Institute of Statistical Mathematics 相似文献
89.
Akinori Kubo Shinsuke Nakahara Ryoichi Iwata Katsuhiro Takahashi Tadashi Arai 《Tetrahedron letters》1980,21(33):3207-3208
A new isoquinolinequinone antibiotic, mimocin(2), has been isolated from the strain of Streptomyces lavendulae. The structure of mimocin has been deduced from mass and PMR spectral data and confirmed by its synthesis. 相似文献
90.