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71.
(+-)-3,3,7-Trimethyl-2,9-dioxatricyclo[4.2.1.04, 7]noname and (+-)-3,3,7-trimethyl-2,9-dioxatricyclo[3.3.1.04, 7] nonane were synthesized. The latter was shown to be (+-)-lineatin, an ambrosia beetle pheromone. 相似文献
72.
Tokuda N Sasaki N Watanabe H Miki K Yamasaki S Hasunuma R Yamabe K 《The journal of physical chemistry. B》2005,109(26):12655-12657
Electroless deposition of Ag on atomically flat H-terminated Si(111) surfaces in aqueous alkaline solutions containing Ag ions produced two different sizes of Ag nanowires along atomic step edges: (1) a narrow nanowire of 10 nm in width and 0.5 nm in height and (2) a wide nanowire of 35 nm in width and 11 nm in height. The narrow and wide nanowires were formed by immersion in the solutions containing less than 1 ppb and 8 ppm dissolved-oxygen concentrations, respectively. This result indicates that the dissolved oxygen initiates the formation of Ag nucleation sites and that the fabrication method has a possibility of controlling the size of Ag nanowires. 相似文献
73.
Synthesis and characterization of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids with a branched-acyl chain 总被引:3,自引:0,他引:3
We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C(4) to C(18), as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C(12), 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant. 相似文献
74.
5-Amino-5-deazaflavin derivatives are newly synthesized by direct coupling of 5-deazaflavins and amines. Some of them revealed potential activity toward tumor cells such as L1210 or KB cells. 相似文献
75.
We examined the hydrolysis mechanism of salicylic acid-tyrosine (salicyl-tyrosine) and salicylic acid-methionine conjugate (salicyl-methionine) in rabbits by exploring their behavior following intraduodenal and intracecal administration (72 and 36 mumol/kg, respectively: salicylic acid equivalent). A large amount of salicyl-methionine was absorbed following intraduodenal administration of salicyl-methionine, without being metabolized to salicylic acid in the small intestinal mucosa. On the contrary, salicylic acid was detected in the blood following intraduodenal administration of salicyl-tyrosine, suggesting that salicyl-tyrosine was metabolized in the small intestinal mucosa. After oral pretreatment of rabbits with kanamycin sulfate (6 x 400 mg) or tinidazole (6 x 160 mg), the hydrolysis of salicyl-tyrosine and salicyl-methionine following intracecal administration was inhibited significantly, indicating that the intestinal microorganisms were responsible for the biotransformation of these prodrugs. Furthermore, in rabbits orally pretreated with both kanamycin sulfate and tinidazole, a significant inhibition of salicylic acid formation from salicyl-tyrosine and salicyl-methionine following intracecal administration was observed. 相似文献
76.
Layer-by-layer assembled multilayer films of titanate nanotubes, Ag- or Au-loaded nanotubes, and nanotubes/nanosheets with polycations 总被引:1,自引:0,他引:1
Aqueous suspensions of hydrothermally synthesized titanate nanotubes and poly(diallyldimethylammonium chloride) (PDDA) have been employed to fabricate multilayer films on various substrates in a layer-by-layer fashion. Atomic force microscopy displays the dense coverage of the substrate surface by the nanotubes. UV-vis absorption spectroscopy confirms the consecutive growth of PDDA/nanotube layer pairs. Single crystalline Ag and Au nanoparticles with narrow size distribution spatially correlating with the nanotubes have been obtained by treating the nanotubes with AgNO(3) or HAuCl(4) aqueous solution followed by chemical reduction. The noble metal nanoparticles show a strong surface plasmon absorption band. A multilayer film construction of the noble-metal-loaded nanotubes has also been achieved. This process has been further extended to the heteroassembly of nanotubes/nanosheets in different layer sequences. 相似文献
77.
(±) - 33,7 - Trimethyl - 2,9 - dioxatricyclo[3.3.1.04,7]nonane 1 and (±) - 3,3,7 - trimethyl - 2,9-dioxatricyclo [4.2.1.04,7]nonane 2 were synthesized. The former was shown to be (±)-lineatin, an ambrosia beetle pheromone. A selective synthesis of (±)-lineatin was devised, which was modified to yield the both enantiomers of lineatin via optical resolution of an intermediate. 相似文献
78.
[reaction: see text] Reaction of gamma-p-toluenesulfonyl-alpha,beta-epoxysilane with alkyl halides and aldehydes followed by treatment with n-Bu4NF affords alpha,beta-unsaturated aldehydes via a Brook rearrangement-mediated tandem process under extremely mild conditions. 相似文献
79.
T Tokumura T Tanaka A Sasaki Y Tsuchiya K Abe R Machida 《Chemical & pharmaceutical bulletin》1990,38(11):3094-3098
The stability and some physicochemical properties of a novel hexapeptide, (Me)Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt (I), with neurotensin activity, were investigated. The degradation of I in aqueous solution was observed as a pseudo-first order reaction. By determining the degradation rate of I at various pH values, it was found that I was most stable at around pH 4. The activation energies of the degradation in aqueous solutions at pH 2.2, 6.1, 7.0 and 8.0 were 16.3, 22.2, 23.9 and 24.2 kcal/mol, respectively. The enzymatic hydrolysis of I was studied in vitro with a porcine liver esterase at 37 degrees C. The degradation of I in this system was observed as a pseudo-first order reaction. The degradation rate of I in the presence of the esterase was about 10000 times larger than the rate in a buffer solution. I in the solid state was stable under 65 degrees C and labilized by strong light and/or high humidity. The pKa1, pKa2 and pKa3 of I were 7.1, 10.0 and 11.3, respectively. The partition coefficients between n-octanol and the buffer solution at pH values ranging from 2 to 11 were measured. The partition coefficient increased with the increase of the pH value. But the value at pH 7.0 was 2.10 x 10(-2), which was very low. The solubility of I in aqueous solution was more than 10 mg/ml. From the results of the powder X-ray diffraction pattern, I in the solid state was found to be amorphous. The dissolution rates in the 1st and 2nd fluid of JPXI at 37 degrees C and 100 rpm were 19.4 and 9.0 mg/cm2.min, respectively. 相似文献
80.
In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed. 相似文献