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991.
Motohiko Hikuma Tatsuru Kubo Takeo Yasuda Isao Karube Shuichi Suzuki 《Analytica chimica acta》1979,109(1):33-38
A microbial sensor consisting of immobilized Trichosporon brassicae, a gas-permeable Teflon membrane and an oxygen electrode is suitable for the continuous determination of acetic acid in fermentation broths. When an acetic acid solution is pumped through the flow system, the current decreases to a steady state with a response time of 8 min; shorter pumping times give peaks which can also be measured. The relationship between the current decrease and the acetic acid concentration is linear up to 54 mg l-1, with a relative standard deviation of about 6% at the higher concentrations. Selectivity is satisfactory. Results obtained with this sensor and by gas chromatography for a glutamic acid fermentation broth were in good agreement (regression coefficient 1.04). The sensor was stable for more than 3 weeks and 1500 assays. 相似文献
992.
Isomerization from cis stilbene derivatives (c-S (S = RCH=CHC(6)H(5): 1, R = C(6)H(5); 2, R = 4-CH(3)C(6)H(4); 3, R = 4-CH(3)OC(6)H(4) (= An); 4, R = 2,4-(CH(3)O)(2)C(6)H(3); 5, R = 3,4-(CH(3)O)(2)C(6)H(3); 6, R = 3,5-(CH(3)O)(2)C(6)H(3); 7, AnCH=C(CH(3))C(6)H(5); 8, AnCH=CHAn)) to trans isomers (t-S) and oxidation of S with O(2) were studied in gamma-ray radiolyses of c-S in Ar-saturated 1,2-dichloroethane (DCE) and of S in O(2)-saturated DCE, respectively. On the basis of product analyses, it is suggested that a smaller barrier to c-t unimolecular isomerization for c-3(*+)-5(*+) and 8(*+) than for c-1(*+), 2(*+), and 6(*+) due to the single bond character of the central C=C double bond for c-3(*+)-5(*+) and 8(*+) with a p-methoxyl group but not for c-1(*+), 2(*+), and 6(*+) without a p-methoxyl group because of the contribution of a quinoid-type structure induced by charge-spin separation. The isomerization proceeds via chain reaction mechanisms involving c-t unimolecular isomerization and endergonic hole transfer or dimerization and decomposition. The isomerization of c-3(*+) to t-3(*+) is catalyzed by addition of 1,4-dimethoxybenzene but terminated by triethylamine. The regioselective formation of 3d in oxidation of 3(*+) with O(2) is explained by spin localization on the beta-olefinic carbon in 3(*+). The results of product analyses are compared with the rate constants of the unimolecular isomerization and the oxidation for S(*+) measured with pulse radiolyses. 相似文献
993.
Tetsuro Shimo Tsuneaki Iwakiri Kenichi Somekawa Takaaki Suishu 《Journal of heterocyclic chemistry》1992,29(1):199-201
Photosensitized cycloaddition reaction of methyl 2-pyrone-5-carboxylate ( 1 ) with 2,3-dihydrofuran gave cis- exo- and cis-endo-[2 + 2] cycloadducts across the C3-C4 double bond in 1 , and a [4 + 2] cycloadduct which was different in addition-orientation from the Diels-Alder adducts. Each [2 + 2] cycloadduct was obtained by the use of sensitizers having different triplet energies. Photosensitized reactions of 1 with 3,4-dihydro-2H-pyrans afforded cis-endo-[2 + 2] cycloadducts, respectively. The photocycloaddition mechanism was also explained from the excited state of 1 calculated by means of MNDO-Cl method. 相似文献
994.
[reactions: see text] Comprehensive studies were carried out on efficient In- or In(I)-based diastereoselective Reformatsky-type reactions of simple ketones, alpha-alkoxy ketones, and beta-keto esters. High anti selectivity was established in the addition of the branched alpha-halo ester derivatives to simple ketones using indium metal under THF-refluxing conditions. The stereochemistry undoubtedly indicated that the involvement of a cyclic transition state, formed from the ketone and stereochemically preferred transient E-enolate derived from the branched alpha-halo ester. Next, with the view of tailoring high degree of stereoselection, the concept of chelation-controlled addition of indium enolates was envisioned. In this line, marvelously syn selective additions to alpha-alkoxy ketones and beta-keto esters were established. Interestingly, these diastereoselective additions to alpha-alkoxy ketones and beta-keto esters require either In(I)X or In-InCl3 systems in toluene under ultrasonication, while very poor efficiency and diastereoselectivity were obtained using indium metal or THF as solvent. The stereochemistry of key products was unambiguously determined by the single-crystal X-ray structure analyses. On the basis of the observed astonishing diastereoselectivities due to strong chelation plausibly, a low-valent RIn(I)-type transient spices could be projected as very reactive spices in the Reformatsky-type reactions. 相似文献
995.
Novel reactions of 7,7-dichloro- and 7,7,8-trichloro-3-oxo-2-oxabicyclo[4.2.0]oct-4-ene-6-carboxylates 5 with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in alcohol gave pyrano[4,3-b]pyran-2,5-diones 8 via (Z)-(2H-pyran-2-on-3-yl)butenoates 7. On the other hand, the same treatment of 7,7,8-trichloro-2-oxo-3-oxabicyclo-[4.2.0]oct-4-ene-5-carboxylate 6b afforded 2-oxo-3-oxabicyclo[4.2.0]oct-4,7-diene-5-carboxylate 14 via cyclobutene formation and SN2′ displacement by attack of the alkoxy anion. 相似文献
996.
Yasushi Koyama Keishi Kubo Mika Komori Haruo Yasuda Yumiko Mukai 《Photochemistry and photobiology》1991,54(3):433-443
Alumina adsorption chromatography and ion-pair reversed-phase chromatography were developed to analyze the isomers of unprotonated and protonated n-butylamine Schiff base of retinal (RSB and PRSB), respectively. Photoisomerization starting from the all-trans, 11-cis and 13-cis isomers was traced for RSB in n-hexane, acetonitrile, methanol and 1-butanol, and for PRSB in methanol, acetonitrile and 1-butanol. The quantum yields of photoisomerization for the all-trans, 9-cis, 11-cis and 13-cis isomers were determined for RSB and PRSB in the above solvents except 1-butanol. On the other hand, photoisomerization of isomeric retinal bound (through Schiff base linkage) to bovine serum albumin (RBSA) in aqueous solution (pH 3, 7 and 12) as well as thermal isomerization of RSB (in n-hexane), PRSB (in methanol) and RBSA (in aqueous solution, pH 7) were traced starting from the all-trans, 11-cis, and 13-cis isomers. Protonation of RSB drastically changes the pathway of photoisomerization and increases the quantum yields of isomeric RSB. The solvent polarity increases the quantum yields of RSB differently depending on the configuration. Protonation enhances thermal isomerization also. The results of the above model systems are compared with those of retinal proteins to rationalize their selection of the particular isomerization pathways. 相似文献
997.
998.
Back Cover: Synthesis and Applications of (ONO Pincer)Ruthenium‐Complex‐Bound Norvalines (Chem. Asian J. 7/2016) 下载免费PDF全文
999.
Masateru Ono Shin Yasuda Kaori Nishi Kazutaka Yamamoto Satoshi Fuchizaki Satomi Higuchi 《Natural product research》2016,30(8):904-911
Two new ursane-type triterpenoids (1, 2) attached to isopropylidenedioxy group were isolated from the seeds of blackberry (Rubus fructicosus L., Rosaceae) along with two known ursane-type triterpenoids, 2,3-O-isopropylidenyl-2α,3α,19α-trihydroxyurs-12-en-28-oic acid (3) and 1β-hydroxyeuscaphic acid (4). The chemical structures of 1 and 2 were determined to be 2,3-O-isopropylidene-1β,2β,3β,19α-tetrahydroxyurs-12-en-28-oic acid and 1,2-O-isopropylidene-1β,2α,3α,19α-tetrahydroxyurs-12-en-28-oic acid, respectively, based on spectroscopic data. Additionally, their cytotoxic activity towards HL-60 human leukaemia cells was evaluated. Among them, 3 demonstrated a clear cytotoxic activity with 72.8 μM of IC50 value. 相似文献
1000.
To clarify the applicability of locally reacting boundary conditions in wave-based numerical analyses of sound fields in rooms, we numerically analyzed a non-diffuse sound field in a room with unevenly distributed sound absorbing surfaces and investigated the differences between the extended and local reactions. Each absorbing surface was a porous material layer backed by a rigid wall. Simulations were performed by the fast multipole boundary element method, a highly efficient boundary element method using the fast multipole method. At low frequencies, the extended and local reactions yielded similar reverberation decay curves because of the influence of the room. However, when the random incidence absorption coefficients were small at low frequencies or frequencies were high, the difference was greater than expected from the corresponding Eyring decay lines. We conclude at high frequencies, the locally reacting boundary conditions lead to a longer reverberation time than that expected from the absorption coefficient differences between the extended and local reactions. These differences were similar in sound-pressure-level and sound-intensity-level distributions, and in the oblique incidence absorption coefficient of the absorbing surfaces, but were increased at low frequencies. 相似文献