共查询到20条相似文献,搜索用时 31 毫秒
1.
Stefan E. Boiadjiev Brian A. Conley Justin O. Brower Antony F. McDonagh David A. Lightner 《Monatshefte für Chemie / Chemical Monthly》2006,137(11):1463-1476
Summary. A set of four regioisomeric dipyrrinone propionic acids has been synthesized and their hepatic metabolism examined in rats:
xanthobilirubinic acid and pseudo-xanthobilirubinic acid each with a propionic acid on a pyrrole ring; exo-ψ-xanthobilirubinic acid and endo-ψ-xanthobilirubinic acid, each with a propionic acid transposed to a lactam ring. After intravenous injection all four isomers
were excreted to some degree in unchanged form in bile in normal rats. Xanthobilirubinic acid, the structurally closest dipyrrinone
to bilirubin, and exo-ψ-xanthobilirubinic acid were excreted almost entirely in unchanged form. However, a small fraction of xanthobilirubinic
acid acyl glucuronide was also detected. More extensive acyl glucuronidation was observed for pseudo-xanthobilirubinic acid,
and endo-ψ-xanthobilirubinic acid underwent slow metabolism to unidentified more polar products that did not seem to be glucuronides. 相似文献
2.
Chockalingam Karunakaran Kaliyaperumal Anandhy Velusamy Ramachandran 《Monatshefte für Chemie / Chemical Monthly》2000,131(10):1025-1029
Summary. Upon aging, perborate in glacial acetic acid generates peracetic acid and thus oxidizes S-phenylmercaptoacetic acid rapidly.
Perborate dissolved in ethylene glycol, however, does not show the aging effect, and the corresponding oxidation proceeds
smoothly. The oxidation is of second order and not acid catalyzed. Boric acid and borate do not influence the oxidation. In
the smooth oxidation, is the reactive species. The oxidation of some para-substituted S-phenylmercaptoacetic acids conforms to the Exner relationship, indicating operation of a common mechanism. Also, the oxidation obeys the Hammett equation with a negative reaction constant. However, the oxidation of p-nitro-S-phenylmercaptoacetic acid follows a different kinetic pathway.
Received March 15, 2000. Accepted (revised) May 3, 2000 相似文献
3.
Vadim A. Pestunovich Nataliya F. Lazareva Alexander I. Albanov 《Monatshefte für Chemie / Chemical Monthly》2006,137(8):1005-1013
Summary. The first representative of the N-silylmethylamides of phosphoric acid O=P[NMe(CH2SiMe
n
(OEt)3-n
]3 have been synthesized by interaction of MeNHCH2SiMe
n
(OEt)3-n
(n = 2, 3) with POCl3. The interaction of the N,N′,N″-trimethyl-N,N′,N″-tris[(ethoxydimethyl- silyl)methyl]triamide phosphoric acid with BF3·Et2O or BCl3 results in the formation of the N,N′,N″-trimethyl-N,N′,N″-tris[(fluorodimethyl-silyl)methyl]triamide phosphoric acid or N,N′,N″-trimethyl-N,N′,N″-tris[(chlorodimethylsilyl)methyl]triamide phosphoric acid. NMR data show on the tetracoordinate state of silicon in these
products.
Professor Vadim Aleksandrovich Pestunovich, our chief, teacher and friend died on July 4th, 2004 相似文献
4.
Summary. Fatty acid oxidation is usually thought of as being a preferred ATP source during sepsis, as shown by the decrease in respiratory quotient in septic patients and animals. However, fatty acid oxidation may be impaired relative to circulating triglyceride levels, resulting in increased cycling between triglycerides and non-esterified fatty acids. The rate of fatty acid oxidation is critically dependent on the stage of sepsis. Carnitine may be depleted during sepsis by a combination of muscle wasting, erythrocyte haemolysis, decreased tissue uptake, reduced kidney reabsorption of free carnitine, and increased excretion of acyl-carnitines. Whether there may be any beneficial effects of carnitine supplementation during sepsis, is, as yet, uncertain. 相似文献
5.
Summary. Three new acyclic dimers of cholic acid with oxamide and isomeric hydrazide (N,N′-diacylhydrazine) spacers were obtained. The oxamide spacers bind two identical steroidal subunits through position 3 (head-to-head
dimer) or position 23 (tail-to-tail dimer). In the case of a third dimer the hydrazine moiety binds two molecules of cholic
acid through position 24 (tail-to-tail dimer). 相似文献
6.
Alberto Macario Prof. Susana Blanco Dr. Javix Thomas Prof. Yunjie Xu Prof. Juan Carlos López 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(53):12325-12331
Four conformers of the heterodimer o-anisic acid–formic acid, formed in a supersonic expansion, have been probed by Fourier transform microwave spectroscopy. Two of these forms have the typical double intermolecular hydrogen-bond cyclic structure. The other two show the o-anisic acid moiety bearing a trans-COOH arrangement supported by an intramolecular O−H⋅⋅⋅O bond to the neighbor methoxy group. In these conformers, formic acid interacts with o-anisic acid mainly through an intermolecular O−H⋅⋅⋅O hydrogen bond either to the O−H or to the C=O moieties, reinforced by other weak interactions. Surprisingly, the most abundant conformer in the supersonic expansion is the complex in which the o-anisic acid is in trans arrangement with the formic acid interacting with the O−H group. Such a trans-COOH arrangement in which the intramolecular hydrogen bond dominates over the usually observed double intermolecular hydrogen bond interaction has never been observed previously in an acid–acid dimer. 相似文献
7.
Seed oils of 15Sideritisspecies collected from different regions in Turkey(S. athoa, S. brevidens, S. caesarea, S. condensata, S. congesta, S. dichotoma, S. erythrantha var. cedretorum, S. germanicopolitana ssp. germanicopolitana, S. hololeuca, S. lanata, S. libanotica ssp. violascens, S. lycia, S. niveotomentosa, S. perfoliata, S. phrygia, S. pisidica)were obtained by a Soxhlet apparatus using hexane. The oil yields were found to be between 5.6-36.3%. Fatty acids in the oils were converted to methyl esters and their compositions were determined by GC/MS. The main fatty acid components of the oils from all the species are linoleic (45.4-64.0%), oleic (12.3-26.5%), 6-octadecynoic (4.5-26.8%), palmitic (0.3-9.4%), and linolenic (0.8-2.0%) acids. 相似文献
8.
Pekka Juusola Pentti Minkkinen Lasse Leino Jarmo K. Laihia 《Monatshefte für Chemie / Chemical Monthly》2007,138(10):951-965
Summary. (E)- and (Z)-Urocanic acids are endogenous chemicals in the normal mammalian skin. The first and the second thermodynamic dissociation
constants (pK
a1 and pK
a2) of urocanic acid isomers were determined using UV spectrophotometry in aqueous solutions. The values with standard deviation
(pK
a1 = 3.43 ± 0.12 and pK
a2 = 5.80 ± 0.04) and (pK
a1 = 2.7 ± 0.3 and pK
a2 = 6.65 ± 0.04) were obtained to (E)- and (Z)-urocanic acids, respectively. The second dissociations were studied also by potentiometric titration in aqueous sodium chloride
solutions up to the isotonic salt concentration (0.154 mol dm−3), and the second thermodynamic dissociation constants as well as activity parameters for both isomers were determined at
temperature 25°C and for (E)-urocanic acid also at 37°C. The obtained pK
a2 values were close to those found by UV spectrophotometry. The equations for the calculation of the second stoichiometric
dissociation constants of urocanic acid isomers on molality and molarity scale in aqueous sodium chloride solutions were derived.
The obtained pK
a1 and pK
a2 values for (Z)-urocanic acid appear to be essentially lower than some previously reported values in literature.
An erratum to this article is available at . 相似文献
9.
Vesna Kuntić Maja Stanojević Ivanka Holclajtner-Antunović Snežana Uskoković-Marković Ubavka Mioč Marija Todorović Tanja Jovanović Vladana Vukojević 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):803-810
Summary. Compounds of phosphotungstic acid (WPA) containing the amino acids alanine (WPA–Ala) or glycine (WPA–Gly) as counter cations were synthesized and characterized by elemental analysis, thermal analysis, and IR spectroscopy. Cellular
toxicity was assessed by the trypan blue exclusion method, and the antiviral activity of WPA and the modified WPA compounds was tested against herpes simplex viruses (HSV) type 1 and type 2. Biological assays indicate that the newly synthesized
compounds exhibit no evident cytotoxic effects on Vero cells and negligible antiviral activity against HSV-1 and HSV-2. 相似文献
10.
Tzuen-Yeuan Lin 《中国化学会会志》1981,28(3):149-154
The chromic acid oxidation of cyclohexanone catalyzed by picolinic acid in water undergoes a change from first-to zero-order dependence in both cyclohexanone and acidity. The mechanism proposed indicates the formation of an intermediate C1 by picolinic acid and chromic acid. Then C1 would react with enol form of cyclohexanone to give another intermediate C2. C2 finally cleaves into products. 相似文献
11.
Summary. The stereoselective syntheses of four unsaturated hydroxy fatty acids 13S,2E,4E,9E)- 13-hydroxy-2,4,9-tetradecatrienoic acid, (13S,9Z,11E)-13-hydroxy-9,11-tetradecadienoic acid, (13S,9E, 11E)-13-hydroxy-9,11-tetradecadienoic acid, and (13S,2E,4E,9E)-13-hydroxy-2,4,9,11-tetradecatrienoic acid, are described. Wittig reactions, regioselective oxidation of dialcohol 3, and diastereomerization were used. 相似文献
12.
Nisar Ullah Werner Seebacher Robert Weis Johann Jurenitsch Katharina Rauchensteiner Ernst Haslinger 《Monatshefte für Chemie / Chemical Monthly》2000,131(7):787-794
Summary. The synthesis of monodesmosidic glycyrrhetic acid disaccharides via its diphenylmethyl ester is described. Their hemolytic activity is lower as compared to the corresponding oleanolic aciddisaccharides.
The influence of the structure of the aglycon on the hemolytic activity is discussed.
Received November 18, 1999. Accepted November 30, 1999 相似文献
13.
Summary. A structurally simplified analogue of the antibiotic (+)-heptelidic acid was synthesized in ten steps with an overall yield
of 9%. Key step was a conjugate addition of a silyl protected vinylcuprate to an asymmetrically shielded enoate, which gave
an adduct as a single diastereomer. Transesterification in the presence of triethylamine allowed a selective cleavage of the
chiral auxiliary and afforded an enantiomerically pure methyl ester. This easily enolizable β-ketoester was transformed to
the trans configurated methylene derivative using a four-step reaction sequence. Finally, the desired epoxylactone was accessible from
the methylene derivative by lactone ring formation and successive oxidation in four steps.
Received July 13, 2001. Accepted August 16, 2001 相似文献
14.
Summary. All-endo-3-amino-5-hydroxybicyclo[2.2.1]heptane-2-carboxylic acid and two epimers of 3-amino-6-hydroxybicyclo[2.2.1]heptane-2-carboxylic
acid were prepared via 1,3-oxazine or γ-lactone intermediates by the stereoselective functionalization of endo-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylic acid derivatives. Their structures were proved by IR and NMR spectroscopy, with
the use of HMQC, HMBC, DEPT, and DIFFNOE techniques. 相似文献
15.
Naohiro Uemura Kento Sano Arisa Matsumoto Yasushi Yoshida Takashi Mino Masami Sakamoto 《化学:亚洲杂志》2019,14(23):4150-4153
The asymmetric synthesis of an aspartic acid derivative, N‐succinopyridine, from prochiral starting materials involving dynamic enantioselective crystallization was accomplished without using any external chiral source. The aza‐Michael addition reaction of prochiral maleic acid and pyridine afforded racemic conglomerate N‐succinopyridine in water. Continuous stirring of the suspension of the reaction mixture with acetic acid promoted gradual deracemization to afford a crystal with an excellent optical purity of 99 % in 71 % yield. 相似文献
16.
Monika Poláková Dušan Joniak Miloslav Ďuriš 《Monatshefte für Chemie / Chemical Monthly》2000,131(11):1197-1205
Summary. Because of the low stability of the benzyl ester linkage in benzyl 1,2:3,5-di-O-benzylidene-α-D-glucofuranuronate during the removal of the benzylidene groups by acid hydrolysis and/or hydrogenolysis, 4-methoxybenzylidene
groups were used to block the free hydroxyl groups of D-glucuronic acid. Several benzyl esters of D-glucuronic acid were prepared, and their relative rates of acid catalyzed hydrolysis were determined by liquid-chromatographic
separation of the reaction mixture and subsequent diode array detection.
Received May 22, 2000. Accepted (revised) July 17, 2000 相似文献
17.
(+)-Pisiferic acid ( 1 ), an antibiotic active against Gram-negative and Gram-positive bacteria, was synthesized starting from dehydroabietic acid ( 2 ) or abietic acid ( 26 ). The terpene ring system was functionalized and a Barton reaction used to oxidize Me(20). The intermediates of this photochemical reaction were isolated and characterized. 相似文献
18.
L-Ascorbic acid and oxalic acid could be successfully separated with a column of 8% cross-linked sulfonated polystyrene cation-exchange resin in hydrogen form, and eluted with 0.01% aqueous solution of nitric acid, sulfuric acid, or phosphoric acid. Among the mineral acids used, nitric acid showed the best separatory effect. The minimum detectable quantities of the acids were 0.05 μg and 0.5 μg per 0.5 ml sample solution for L-ascorbic acid and oxalic acid, respectively. Under this condition, the acids could be detected by using automatic UV-monitor apparatus. 相似文献
19.
Loutfy H. Madkour Amera M. Hassanein Mohamed M. Ghoneim Safwat A. Eid 《Monatshefte für Chemie / Chemical Monthly》2001,132(2):245-258
Summary. The inhibition of corrosion of iron in 2 M nitric acid and 2 M sulfuric acid solutions by substituted phenylhydantoin, thiohydantoin, and dithiohydantoin compounds was measured using thermometric,
weight loss, and polarization methods. The three methods gave consistent results. The polarization curves indicated that the
hydantoin compounds act as mixed-type inhibitors. The adsorption of the inhibitors were found to obey the Temkin adsorption isotherm. The higher inhibition efficiency of the additives in nitric with respect to sulfuric acid solution may
be attributed to the reduced formation of soluble quaternary nitrogen salts in nitric acid medium, favouring adsorption of
the parent additive on the metal surface. The obtained results indicate that the corrosion rate of iron in both acids increases
with increasing temperature, both in absence and presence of the tested inhibitors. Kinetic-thermodynamic model functions
and Temkin isotherm data are compared and discussed. The synergistic effect of halide anions on the inhibition efficiency of the hydantoin
compounds was also investigated.
Received June 5, 2000. Accepted (revised) September 13, 2000 相似文献
20.
Zhenyuan Zhu Shengfeng Li Rongqiang Liu Jing Yuan Haibiao Wang Yongmin Zhang Yang Liu 《中国化学》2010,28(11):2245-2248
This paper describes an efficient synthesis of carbohydrate fatty acid esters based on a highly stereo‐ and regio‐selective esterification. The suitably protected glycosyl was esterified with stearic acid to give mainly the β‐anomer in good yield using p‐toluenesulfonic acid as catalyst. The structures of these compounds were fully confirmed by 1H, 13C NMR, mass spectra and HRMS. 相似文献