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251.
252.
T Maruyama Y Sato T Horii H Shiota K Nitta T Shirasaka H Mitsuya M Honjo 《Chemical & pharmaceutical bulletin》1990,38(10):2719-2725
9-Cyclobutyladenine (4a), cis- and trans-9-[3- (hydroxymethyl)cyclobutyl]adenine (4b) and 9-[3,3-bis(hydroxymethyl)cyclobutyl]adenine(4d) were prepared from the corresponding cyclobutylamine derivatives (1a, 1b and 1d). Guanine congeners (9a, cis- and trans-9b and 9d) and carbocyclic oxetanocin G (1',2'-trans-9f) were also prepared. Carbocyclic oxetanocin A(1',2'-trans-4f), the preparation of which we have already published, and G were found to be active against herpes simplex virus (type 1 and 2) in vitro, while cis-4b and cis-9b showed an in vitro antiretroviral activity against human immunodeficiency virus (type 1). 相似文献
253.
In order to improve the thermal stability of colored merocyanine formed by the photochromic reaction of spironaphthoxazine, the spiro compound was incorporated in polymeric siloxanes. They are liquid poly(methylphenylsiloxane) and solid methyl‐ or phenyl‐siloxane resins prepared by the hydrolysis and condensation reactions of the corresponding di‐ or tri‐ethoxysilane. To the polymers the spirooxazine moiety isbonded covalently. Higher stability of the colored form was not observed in the liquid polysiloxane, but in the solid resins. The phenyl substituent in the resin is more effective than the methyl one for stabilization, suggesting that the bulky substituent in the vicinity of the spirooxazine moiety is important as well as stiff polymer matrices. The phenylsiloxane resin with the spirooxazine moiety was enclosed in rigid sol–gel silica, but a further improvement of the thermal stability was not observed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
254.
Yuko Chihara Hidetoshi Arima Masayo Arizono Koki Wada Fumitoshi Hirayama Kaneto Uekama 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(1-2):89-93
Interactions in aqueous dispersion between dipalmitoyl phosphatidyl choline (DPPC) liposomes and dissolved cyclodextrins (CD)
of different chemical compositions, respectively, were studied. Liposomal dispersions with small unilamellar vesicles (SUV)
of monomodal size distribution were prepared and the physical stability of the vesicles both in the presence and absence of
cyclodextrin was investigated. For the characterization of the kinetic stability of the dispersions under various conditions,
size-distribution functions determined by photon-correlation spectroscopy (PCS) were used. The affinity of cyclodextrins to
the liposomes was characterized by ‚binding isothermsȁ9 determined under equilibrium conditions at 25 °C. Based on the quantity
of the cyclodextrins bound to the DPPC bilayers, stability constants for the associates were estimated. The physical stability
of the liposomes and the possible control of stability were also investigated. 相似文献
255.
The cloud temperature of 2 wt% C(12)EO(8) aqueous solutions decreases upon addition of sarcosinate-lauroyl isopropyl (SLIP), 1-dodecanol, and m-xylene, whereas it increases in glycerol tris(2-ethylhexanoic) ester (TEH), isopropyl myristate (IPM), and saturated hydrocarbon systems. A three-phase microemulsion is formed at equal weights of water and oil in the IPM system, but a lamellar liquid crystal (L(alpha)) is present in the SLIP system at the balanced temperature. The effect of added oil on the phase transition of the hexagonal (H(1)) phase was also investigated by means of SAXS study. The H(1)-L(alpha) transition occurs upon addition of SLIP or 1-dodecanol whereas the H(1)-I(1) (discontinuous micellar cubic) phase transition takes place in TEH or IPM systems. These differences in phase behavior are attributed to the placement of solubilized oil in micelles: In the former systems, oil tends to penetrate in the surfactant palisade layer and induces the surfactant layer curvature in micelles to be less positive, while the penetration tendency is small and the opposite effect on the curvature is induced upon addition of the latter oils. Copyright 2001 Academic Press. 相似文献
256.
Hidetoshi Yamada Koki Tanigakiuchi Kohei Nagao Kotaro Okajima Tatsuya Mukae 《Tetrahedron letters》2004,45(50):9207-9209
The pyranose rings of the 2,3-bis-O-tert-butyldiphenylsilyl-α- and β-d-glucopyranoses, and of the 2,3-bis-O-tert-butyldimethylsilyl-β-d-glucopyranose were in the 1C4 form. These findings indicate that the introduction of bulky silyl protecting groups at the 2- and 3-positions can flip a pyranose ring into the axial-rich chair form. Previous such ring inversions have been carried out by the silyl protections at the 3- and 4-positions. 相似文献
257.
2-Phenylheptamethyltrisilane as a model compound of polysilastyrene was irradiated at a high dose (1440 kGy) of γ-rays without any additive. The trisilane was found to be resistant to γ-rays, while it gave small amounts of Me6Si2, Me3SiSiMe2Ph, Me3SiH, Me3SiSiHMePh and (Me3Si)2 SiMeC6H4SiMe3. These products can be interpreted as being due to a chain contraction of the trisilane with the extrusion of methylphenylsilylene, a methyl migration with the extrusion of dimethylsilylene, a scission of an Si–Si bond due to an attack by hydrogen atoms, and a substitution of a hydrogen atom on the phenyl group by a trimethylsilyl radical. The same reactions, except the chain contraction, are observed in the cases of pentamethylphenyldisilane and 1,2-diphenyltetramethyldisilane. On the basis of the data obtained, the chemical behavior of polysilastyrene during the irradiation is discussed. 相似文献
258.
Yasuaki Takeuchi Koki Ohno Masasuke Yoshida Kei Nagano 《Photochemistry and photobiology》1981,33(4):587-592
Abstract— Light-induced proton release and uptake by acetylated and unmodified bacteriorhodopsin were measured. Bacteriorhodopsin, when illuminated, shows a net proton release at neutral and alkaline pH's, but in acidic pH, it shows an uptake of protons. In the presence of high concentrations of guanidine hydrochloride, light caused only proton release even in acidic pH and the maximum extent of the release was one proton per bacteriorhodopsin molecule around pH 8.
Acetylation of bacteriorhodopsin caused no alteration in the absorption spectrum of purple complex (bR570 ) and M412 -intermediate, but decreased the decay rate of the M412 -intermediate. Light-induced release of protons was not observed even in neutral pH values, and only the proton uptake was noticed by acetylated purple membrane fragments. In high concentrations of guanidine hydrochloride, no proton uptake or release by illumination was observed. Vesicles were reconstituted from acetylated purple membrane. These vesicles had almost no ability for light-induced proton transport. The role of amino group(s) in light-induced proton release and transport through the purple membrane is discussed. 相似文献
Acetylation of bacteriorhodopsin caused no alteration in the absorption spectrum of purple complex (bR
259.
Morphology control of poly(2‐oxy‐6‐naphthoyl) (PON) was examined by using reaction‐induced crystallization of oligomers during direct polycondensation of 2‐hydroxy‐6‐naphthoic acid with p‐toluenesulfonyl chloride and N,N‐dimethylformamide in pyridine. PON particles were obtained of which the diameter was in the range of 8.0–8.3 µm. The particles were comprised of many lamellae and exhibited spherulitic morphology. They possessed high crystallinity evaluated from wide‐angle X‐ray scattering (WAXS). Formation mechanism of the particles was clarified from the results of morphology observation, yield, density and WAXS. When the number average degree of polymerization of the oligomers exceeded a critical value of ca. 4–5, they were precipitated to form lamellae. The lamellae grew to spherulites through screw dislocation with continuous precipitation of the oligomer from the solution. Finally, further polymerization occurred gradually in the precipitates. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
260.
An oligonucleotide of triazole‐linked RNA (TLRNA) was synthesized by performing consecutive copper‐catalyzed azide‐alkyne cycloaddition reactions for elongation. The reaction conditions that had been optimized for the synthesis of 3‐mer TLRNA were found to be inappropriate for longer oligonucleotides, and the conditions were reoptimized for the solid‐phase synthesis of an 11‐mer TLRNA oligonucleotide. Duplex formation of the 11‐mer TLRNA oligonucleotide was examined with the complementary oligonucleotide of natural RNA to reveal the effects of the 2′‐OH groups on the duplex stability. 相似文献