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181.
182.
Dr. Ryukou Izumi Dr. Takahiko Matsushita Dr. Naoki Fujitani Dr. Kentaro Naruchi Dr. Hiroki Shimizu Dr. Sakae Tsuda Dr. Hiroshi Hinou Prof. Dr. Shin‐Ichiro Nishimura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(12):3913-3920
Microwave‐assisted solid‐phase synthesis allows for the rapid and large‐scale preparation and structure–activity characterization of tandem repeating glycopeptides, namely monodispersed synthetic antifreeze glycopeptides (syAFGPs, H‐[Ala‐Thr(Galβ1,3GalNAcα1→)‐Ala]n‐OH, n=2–6). By employing novel AFGP analogues, we have demonstrated that of the monodispersed syAFGPn (n=2–6, degree of polymerization, DP=2–6, Mw=1257–3690 Da), syAFGP5 (DP=5, Mw=3082 Da) and syAFGP6 (DP=6, Mw=3690 Da) exhibit the ability to form typical hexagonal bipyramidal ice crystals and satisfactory thermal hysteresis activity. Structural characterization by NMR and CD spectroscopy revealed that syAFGP6 forms a typical poly‐L ‐proline type II helix‐like structure in aqueous solution whereas enzymatic modification by sialic acid of the residues at the C‐3 positions of the nonreducing Gal residues disturbs this conformation and eliminates the antifreeze activity. 相似文献
183.
In As-Se-(S)-Ge amorphous films, the chemical etching rate between the heat treated and the light irradiated states differs as well as the optical properties do. A relief-type grating made by the etching has a high diffraction efficiency (∽15%). The diffraction efficiency of the relief-type grating is analyzed by a Fourier expansion method under some assumptions and good agreement is obtained between the calculated and the experimental values. 相似文献
184.
Treatment of cinnamyl, 3-methyl-2-butenyl, and 2-cyclohexenyl phenyl tellurides with an oxidizing agent such as H2O2, NaIO4 or t-BuOOH at room temperature under nitrogen affords 1-phenyl-2-propenol, 2-methyl-3-butene-2-ol, and 2-cyclohexenol as a sole or main product respectively in a high yield. The formation of these allylic alcohols can be best explained by assuming a [2,3]-sigmatropic rearrangement of the intermediate allylic telluroxides. These tellurides also react with oxygen, the formation of α.β-unsaturated carbonyl compounds being much increased in this oxidation. 相似文献
185.
Abe K Amako K Arai Y Asano Y Chiba M Chiba Y Daigo M Emura T Endo I Fukawa M Fukui T Fukushima Y Haba J Haidt D Hayashibara I Hemmi Y Higuchi M Hirose T Hojo Y Homma Y Hoshi Y Ikegami Y Ishihara N Kamitani T Kanematsu N Kanzaki J Kikuchi R Kondo T Koseki T Kurashige H Matsui T Minami M Miyake K Mori S Nagashima Y Nakamura T Nakano I Narita Y Odaka S Ogawa K Ohama T Ohsugi T Okamoto A Ono A Osabe H Oyama T Saito H Sakae H Sakamoto H Sakamoto S Sakano M Sakuda M Sasao N Sato M Shioden M Shirai J 《Physical review letters》1989,63(17):1776-1779
186.
Matsumura S Maeda Y Nishimura T Uemura S 《Journal of the American Chemical Society》2003,125(29):8862-8869
A novel enantioselective C-C bond cleavage has been achieved using palladium catalysts and chiral N,P-bidentate ligands in the asymmetric arylation, vinylation, and allenylation of tert-cyclobutanols. In these reactions, the enantioselective beta-carbon elimination of Pd(II) alcoholate formed in situ is the key step. Treatment of tert-cyclobutanols with arylating reagents in toluene in the presence of Pd(OAc)(2), a chiral ferrocene-containing N,P-bidentate ligand, and Cs(2)CO(3) affords optically active gamma-arylated ketones in excellent yields with high enantioselectivity (up to 95% ee). When vinylating reagents are used in place of arylating ones, the asymmetric vinylation also proceeds to afford optically active gamma-vinylated ketones in high yields with good to high enantioselectivity. When propargylic acetates are used, which are known to generate (sigma-allenyl)palladium complexes with Pd(0) species, asymmetric allenylation occurs to afford optically active gamma-allenylated ketones in moderate to good yields with moderate to high enantioselectivity. 相似文献
187.
Two different types of counter-current chromatographs, the cross-axis coil planet centrifuge (X-axis CPC) and horizontal flow-through coil planet centrifuge (horizontal CPC), were evaluated for protein separation with an aqueous-aqueous two-phase polymer system. The sample solution, containing 10-200 mg each of cytochrome c, myoglobin, ovalbumin and hemoglobin in 2 ml of each phase was eluted with the lower phase. In both instruments, the effects of the flow-rate, revolution speed, and parameter beta (helical diameters of the multilayer coil) on the protein separation were investigated. The best results were obtained from the X-axis CPC operated at 750 rpm and a flow-rate of 2.0 ml/min using a multilayer coil with a small helical diameter (beta = 0.25-0.60). Four protein samples were well resolved in less than 5 h. 相似文献
188.
[RuCl2(CO)3]2 catalyzes intermolecular cyclopropanation of various alkenes with propargylic acetates to give vinylcycloropanes in good yields. The key intermediate of this reaction is a vinylcarbene complex generated by nucleophilic attack of the carbonyl oxygen of the acetate to an internal carbon of alkyne activated by the ruthenium complex. 相似文献
189.
Glycidyl ethers of poly(propylene glycol) (PPG) 200, 400 or 950 were oxirane-coupled with several kinds of agarose bead as the bonded phase of packing materials. An eluent was composed of 0.09 M phosphate-buffered 2% (w/w) dextran T40 solution at pH of respective isoelectric points of human blood cells. A linear relationship was found between the retention volumes of platelets, granulocytes and lymphocytes on the PPG-agarose columns and a measure of surface hydrophobicities of the cells, delta log K values, which were determined by using hydrophobic affinity partition. Furthermore, the retention volumes of granulocytes and lymphocytes increased according to the increase of delta log K of PPG-agarose beads. The retention of these two cells must be due to the hydrophobic interaction with the bonded PPG phase. 相似文献
190.
Ichikawa M Takahashi M Aoyagi S Kibayashi C 《Journal of the American Chemical Society》2004,126(50):16553-16558
The first total syntheses of new monoterpene alkaloids (-)-incarvilline, (+)-incarvine C, and (-)-incarvillateine, corresponding to the natural enantiomers, have been accomplished. The strategy for the synthesis of these natural products utilized 6-epi-incarvilline as a common precursor, which was assembled by a three-component coupling reaction using (4S)-4-siloxy-2-cyclopenten-1-one to construct an appropriately trisubstituted cyclopentanone, followed by ring closure to the cis-perhydro-2-pyrindine skeleton by means of a reductive Heck-type reaction. Furthermore, topochemically controlled [2 + 2] photodimerization of cinnamic acid derivatives in the solid state for the stereospecific construction of a 1,2,3,4-tetrasubstituted cyclobutane ring was also investigated as a means to access (-)-incarvillateine. 相似文献