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11.
Toshiyuki Uryu Toshiyuki Seki Tokiji Kawamura Akashi Funamoto Kei Matsuzaki 《Journal of polymer science. Part A, Polymer chemistry》1976,14(12):3035-3044
The stereoregularity of polystyrene prepared by anionic polymerization was determined by means of 13C-NMR spectroscopy. The stereoregularity changed with such polymerization conditions as catalyst, solvent, and temperature. Sodium naphthalene as catalyst gave a syndiotactic-rich polystyrene of 66–68% syndiotactic dyads independently of solvent and temperature, while potassium and cesium naphthalenes as catalyst produced polystyrenes with different stereoregularities ranging from syndiotactic-rich to isotactic-rich configurations, depending on solvent and temperature. The mechanism of anionic polymerization which caused the difference in stereoregularity was discussed from the viewpoint of growing ionic species. 相似文献
12.
Hasegawa E Takizawa S Iwaya K Kurokawa M Chiba N Yamamichi K 《Chemical communications (Cambridge, England)》2002,(17):1966-1967
Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols. 相似文献
13.
Otaka A Watanabe J Yukimasa A Sasaki Y Watanabe H Kinoshita T Oishi S Tamamura H Fujii N 《The Journal of organic chemistry》2004,69(5):1634-1645
A samarium diiodide (SmI(2))-mediated reduction of gamma,gamma-difluoro-alpha,beta-enoates (15, 29, and 34) was successfully applied to the synthesis of (Z)-fluoroalkene dipeptide isosteres (23, 30, and 35), which have served as potential dipeptide mimetics. Reduction of the gamma,gamma-difluoro-alpha,beta-enoates by SmI(2) proceeded via successive two-electron transfers to form dienolate species which upon kinetically controlled trapping with t-BuOH yielded Xaa-Gly-type fluoroalkene isosteres exemplified by 23, 30, and 35. Replacement of the t-BuOH kinetic trapping agent with aldehydes or ketones provided access to alpha-substituted fluoroalkene isosteres (43 and 45) through aldol reactions of Sm-dienolates with the carbonyl compounds. Of particular note, the use of the SmI(2)-HCHO reagent system with chiral enoate 34 provided D-Phe-psi[(Z)-CF[double bond]CH]-D/L-Ser isosteres (45), which could be converted to enantiomerically pure isosteres (49-52) that bore a variety of side chain functionalities at the alpha-position. This was achieved by a sequence of manipulations consisting of beta-lactone formation followed by chromatographic separation and ring-opening with soft nucleophiles. Included in the present work is the first utilization of a Rh-catalyzed Reformatsky reaction of chiral imines for the stereoselective preparation of alpha,alpha-difluoro-beta-amino acid derivatives (28 and 33). The appropriate choice of reagents (carbonyl compounds for kinetic trapping or ring-opening nucleophiles and imines for Reformatsky reactions) allows the presented methodology to yield various fluoroalkene isosteres possessing a wide range of side chain functionalities. 相似文献
14.
Oishi S Kamano T Niida A Odagaki Y Tamamura H Otaka A Hamanaka N Fujii N 《Organic letters》2002,4(7):1051-1054
[reaction: see text] Acyclic psi[(E)-CH=CMe]- and psi[(Z)-CH=CMe]-type dipeptide isosteres were efficiently synthesized. In a key reaction, alpha-alkylation of gamma-mesyloxy-beta-methyl-alpha,beta-unsaturated esters with organocyanocuprates in diethyl ether or tetrahydrofuran preferentially afforded the psi[(E)-CH=CMe]- or psi[(Z)-CH=CMe]-isomer, respectively, via anti-S(N)2' mechanism. 相似文献
15.
Manabe K Iimura S Sun XM Kobayashi S 《Journal of the American Chemical Society》2002,124(40):11971-11978
Dehydration reactions in water have been realized by a surfactant-type catalyst, dodecylbenzenesulfonic acid (DBSA). These reactions include dehydrative esterification, etherification, thioetherification, and dithioacetalization. In these reactions, DBSA and substrates form emulsion droplets whose interior is hydrophobic enough to exclude water molecules generated during the reactions. Detailed studies on the esterification revealed that the yields of esters were affected by temperature, amounts of DBSA used, and the substrates. Esters were obtained in high yields for highly hydrophobic substrates. On the basis of the difference in hydrophobicity of the substrates, unique selective esterification and etherification in water were attained. Furthermore, chemospecific, three-component reactions under DBSA-catalyzed conditions were also found to proceed smoothly. This work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water. 相似文献
16.
Yoshinori Tominaga Hiroto Okuda Shinya Kohra Hisako Mazume 《Journal of heterocyclic chemistry》1991,28(5):1245-1255
Reaction of various types of enaminones, which are prepared by the condensation of 1,3-dicarbonyl compounds with aromatic amines, with carbon disulfide in the presence of sodium hydroxide as the base in dimethyl sulfoxide to give the corresponding enamino dithiocarboxylates, 1,3-thiazines and trithiones. Enamino dithiocarboxylates are cyclized under refluxing in diphenyl ether to give the fused quinoline derivatives. The reaction of 6-arylamino-1,3-dimethyluracils with excess carbon disulfide in the presence of sodium hydroxide and subsequent methylation with dimethyl sulfate gave directly the corresponding 1,3-dimethyl-5-methylthiopyrimido[4,5-b]quinoline-2,4(1H,3H)-diones. 相似文献
17.
A. Kuboyama S. Y. Matsuzaki 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):755-764
The complex formation between cyclodextrins (-, -, -CD's and dimethyl-\-CD) and quinones (three 9, 10-anthraquinone sulphonates and two 1,4-naphthoquinones) in the water-ethylene glycol 1:1 mixture solution at 77 K was investigated using the n* phosphorescence spectra and their excitation spectra and lifetimes of the quinones. It was concluded on the basis of the experimental results that the complexes have various structures according to the CD-quinone combination used. Vitamin K3 was found to form the photodimer very efficiently in the presence of -CD. The assumed CD:quinone ratios of the complexes are given. 相似文献
18.
Matsuura K Ikoma S Sugiyama M Funauchi M Sinohara H 《Applied biochemistry and biotechnology》2000,83(1-3):107-114
Polyclonal Immunoglobulin (Ig) G from patients with rheumatoid arthritis (RA) and healthy subjects hydrolyzed carbobenzoxy−Val−Gly−Arg
p-nitroanilide and D−Pro−Phe−Arg p-nitroanilide. RA IgG exhibited higher activity against the former substrate, but not the latter. On the other hand, RA IgG
showed reduced activity against D−Pro−Phe−Arg methylcoumarinamide, when compared with those of the healthy controls. These
results suggest that RA IgGs differ from normal IgGs in the substrate specificity of amidase activity. Preliminary studies
have shown that two out of three RA IgG samples cleaved a pentapeptide—Gln−Arg−Arg−Arg−Ala−Ala— which is assumed to be associated
with the risk of developing RA (Gregersen, P. K. et al. (1987), Arthritis Rheum.
30, 1205–1213). By contrast, virtually no cleavage of the same peptide was observed with IgG from healthy controls. A peptide
analog, Gln−Arg−Arg−Trp−Ala, was not cleaved at all by any IgGs examined either from RA patients or healthy controls. 相似文献
19.
Kubo Y Tokita S Kojima Y Osano YT Matsuzaki T 《The Journal of organic chemistry》1996,61(11):3758-3765
A new family of indoaniline-derived calix[4]arenes has been synthesized for the purpose of developing a new chromogenic receptor. A condensing reaction of calix[4]arene (1) with 4-(diethylamino)-2-methylaniline hydrochloride (2) in the presence of an oxidizing agent under alkaline conditions affords mono- (3), 1,2-bis- (4), 1,3-bis- (5), and tetrakisindoaniline-derived (6) calix[4]arenes after careful column chromatography. Compound 3 is crystallized from a CHCl(3)-MeOH solution, and the crystal structure was determined by X-ray analysis. The crystal is monoclinic, space group P2(1)/n, Z = 4, a = 19.507(6) ?, b = 18.591(6) ?, c = 8.524(2) ?, beta = 94.69(2) degrees. The final R value for 2406 reflections of F(o) > 3sigma(F(o)) is 0.085. A unique intramolecular hydrogen-bonding network involving the carbonyl oxygen of indoaniline for 3 implied that the quinone carbonyl group as an acceptor of the chromophore can easily be subjected to an electrostatic interaction in the lower rim. Indeed, 1,3-bis(indoaniline)-derived 2,4-bis((ethoxycarbonyl)methoxy)calix[4]arene 7, prepared by the reaction of 5 with ethyl bromoacetate in the presence of NaH, is capable of undergoing an efficient ion-dipole interaction between the binding cation and the two quinone carbonyl groups of the chromophores, so that a selective Ca(2+)-induced pronounced color change (wavelength change > 100 nm) occurs with an association constant on the order of 10(6) in 99% EtOH, making 7 of potential use as an optical sensor for Ca(2+) detection. The IR and NMR studies have indicated that Ca(2+) is encapsulated in the cavity made by the distally located OCH(2)CO(2) groups on the lower rim of the cone-shaped calix[4]arene segment. Interestingly, however, the shape of the cavity in which Ca(2+) has been encapsulated does not have a C(2) axis of symmetry, as inferred from the (1)H-(1)H COSY experiment. On the other hand, 1,2-bis(indoaniline)-derived analogue 8 shows no response with metal ions, which can be interpreted to mean the absence of a cavity for encapsulation on the lower rim. 相似文献
20.
A. Fukumi I. Endo T. Horiguchi Y. Ishida T. Kondo T. Kuwamoto H. Matsuzaki T. Nakamura T. Takahashi 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,42(4):243-249
Systematic study of hyperfine structures, Zeeman and Stark effects in Sm I is performed for the lowest 7G1-6 levels belonging to the configuration 4f 66s6p by atomic-beam laser spectroscopy with fluorescence detection. The hyperfine coupling constants of 7G2-6 levels are determined. From the Zeeman splittings for the 4f 66s 2 7F2-6 ? 4f 66s6p 7G2-6 transitions, g-values are determined for the 7G2.6 levels and the precision is improved by several orders of magnitude. From the Stark splittings for the 7F0-3 ? 7G1-3 transitions, tensor polarizabilities α 2(J) are determined for the upper 7G1-3 levels. Particularly for the 7G1 level (15 650.55 cm?1) which has close-lying opposite-parity level, the isotope dependence of α 2(J) is clearly observed for the first time. 相似文献