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71.
Tsann-Long Su Yu-Kun Yang Jai-Tung Huang Wu-Yun Ren Kyoichi A. Watanabe Ting-Chao Chou 《Journal of heterocyclic chemistry》1993,30(5):1437-1443
This paper is dedicated to the memory of Professor Roland K. Robins The synthesis of 4-[(1,3-diaminopyrrolo[3′,4′:4,5]pyrido[2,3-d]pyrimidin-8-yl)benzoyl]-L-glutamic acid ( 18 ), a potential antifolate and anticancer agent, has been achieved starting from 1,4-dibromobutan-2-ol with alkyl p-aminobenzoic acids. Condensation of these two agents gave 1-(4-alkoxycarbonylphenyl)pyrrolidin-3-ols 7a,b , which were oxidized to the corresponding pyrrolidin-3-one derivatives 8a,b . Compounds 8a,b were converted into 1,3-diamino-8-(4-alkoxycarbonylphenyl)-7,8-dihydro-9H-pyrrolo[3′,4′:4,5]pyrido[2,3-d]pyrimidines 12a,b in 4 steps. Saponification of 12b the benzoate ester and coupling with di-tert-butyl glutamate afforded a mixture of 7,8-dihydro product 16 and its aromatized derivative 17 . Finally hydrolysis of esters 16 or 17 gave only the title compound 18 . The 7,8-dihydro tricyclic derivatives were easily air-oxidized to form their fully aromatized compounds. The title compound 18 was one tenth less active than MTX against HL-60 cells in culture. 相似文献
72.
Two tetrahydrofuran-based γ-amino acids [2,4-cis and 2,4-trans] were subjected to iterative peptide-coupling procedures to afford dimeric, tetrameric and hexameric carbopeptoids in good yield. These homooligomers were prepared for secondary structural study—to ascertain the conformational preference inherent in the monomer units. The l-xylo oligomers were protected with triethylsilyl ethers to increase the range of solvents suitable for structural investigation. Initial secondary structure data indicate the presence of hydrogen-bonded conformations in the l-ribo series. 相似文献
73.
三辛基氧化膦(TOPO)萃取铟的研究 总被引:2,自引:0,他引:2
本文研究了三辛基氧化膦(TOPO)自盐酸溶液中萃取铟的性能,其萃取率是随酸度的增加而增加。与P_(350)和TBP相比较,萃取能力大小顺序为:TOPO>P_(350)>TBP经斜率法和化学分析法研究确定,TOPO白盐酸溶液中萃取铟的反应为:In_((a))~(3+)+H_((a))~++4Cl_((a))~-+2TOPO_((o))F(?)HInCl_4·2TOPO_((o))IR和NMR研究证明:铟是以H[InCl_4]形式被萃入TOPO有机相中的。 相似文献
74.
Cellulose acetate (CA) ultrafiltration hollow fibers were spun via the dry-jet wet spinning technique. The effect of the take-up speed on the mechanical properties, morphology, thermal properties, pure water permeation, retention, and surface characterization of hollow fiber membranes were investigated. Both the inner and outer diameters of the hollow fiber decreased with the increase of take-up speed. Macrovoids were observed on the inner surface of the drawn hollow fibers. The d-space decreased with the increase of the take-up speed. The ultimate tensile stress (UTS) increased and the breaking elongation decreased with the increase of take-up speed. The permeation performance was measured. The hydraulic permeability increased and the retention decreased slightly with the increase of the take-up speed. The surface roughness increased with the increase of the take-up speed. The thermal analysis results showed that the endothermic peak shifts to the higher temperature region and coefficient of thermal expansion (CTE) decrease for a higher take-up speed. 相似文献
75.
Retbøll M Edwards AJ Rae AD Willis AC Bennett MA Wenger E 《Journal of the American Chemical Society》2002,124(28):8348-8360
A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr[o-C(6)H(4)B(pin)]L(2)] (M = Ni, L(2) = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L(2) = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KO(t)Bu to form the corresponding benzyne complexes [M(eta(2)-C(6)H(4))L(2)] (M = Ni, L(2) = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L(2) = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KO(t)Bu, but in this case disproportionation of the initially formed eta(2)-C(6)H(4) complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(mu(2)-C(6)H(4))Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C(6)H(4)C(6)H(4))(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species. 相似文献
76.
Commodari F Khiat A Ibrahimi S Brizius AR Kalkstein N 《Magnetic resonance in chemistry : MRC》2005,43(7):567-572
The NMR-derived solution structure of trans-3,4',5-trihydroxystilbene (resveratrol) was compared with two recent literature crystal x-ray structures, resveratrol in complex with human transthyretin (TTR-RES) from 1DVS.pdb and resveratrol bound to chalcone synthase (CHS-RES) from 1CGZ.pdb. 1H and 13C NMR spectra of resveratrol were acquired in DMSO-d6. Assignments were obtained from an analysis of DQF-COSY, TOCSY, DEPT, HMQC/HSQC, HMBC and INADEQUATE NMR spectra. Past 1H and 13C NMR literature assignments are corrected. The dihedral angle 2-1-1'-2' provides an indication of the relative spatial orientation of the two phenolic rings. Values of 1.62, - 54.10 and 12.6 +/- 1.1 degrees were found for the 1DVS.pdb, 1CGZ.pdb and NMR resveratrol structures, respectively. The 1DVS.pdb resveratrol structure is 'flat' with the two phenolic rings along the same plane. The 1CGZ.pdb structure has these two rings almost orthogonal to each other, and the NMR structure has these two rings much closer to being along the same plane. The angles 1-alpha--alpha' and 1'-alpha'--alpha are along the same trace and of similar magnitude for the 1CGZ.pdb and NMR resveratrol structures. For the 1DVS.pdb resveratrol structure, these angles are about 7-10 degrees greater, with alpha and alpha' being 180 degrees out-of-phase from the other two structures. The alpha rings did not overlap, with the NMR result representing a 'median model' of the two x-ray structures. 相似文献
77.
Zeng W Wang AQ Fisher AL Musson DG 《Rapid communications in mass spectrometry : RCM》2003,17(22):2475-2482
A generic high-throughput liquid chromatography (HTLC) tandem mass spectrometry (MS/MS) assay for the determination of compound I in human urine and dialysate (hemodialysis) was developed and validated. By using the HTLC on-line extraction technique, sample pretreatment was not necessary. The sample was directly injected onto a narrow bore large particle size extraction column (50 x 1.0 mm, 60 microm) where the sample matrix was rapidly washed away using a high flow rate (5 mL/min) aqueous mobile phase while analytes were retained. The analytes were subsequently eluted from the extraction column onto an analytical column using an organic-enriched mobile phase prior to mass spectrometric detection. The analytes were then eluted from the analytical column to the mass spectrometer for the determination. The linear dynamic range was 2.0-6000 ng/mL for the urine assay and 0.1-300 ng/mL for the dialysate assay. Intraday accuracy and precision were evaluated by analyzing five replicates of calibration standards at all concentrations used to construct the standard curve. For the urine assay, the precision (RSD%, n=5) ranged from 1.9 to 8.0% and the accuracy ranged from 87.8 to 105.2% of nominal value. For the dialysate assay, the precision (RSD%, n=5) ranged from 1.1 to 10.0% and the accuracy from 94.5 to 105.2% of nominal value. In-source fragmentation of the acyl glucuronide metabolite (compound III) did not interfere with the determination of parent compound I. The developed HTLC/MS/MS methodology was specific for compound I in the presence of compound III. Column life-time is increased and sample analysis time is decreased over traditional reversed-phase methods when direct injection assays for urine and dialysate are coupled with the technology of HTLC. 相似文献
78.
The binding of single-stranded DNAs and a neutral DNA analogue (peptide nucleic acid, PNA) to single-walled carbon nanotubes in solution phase has been probed by absorbance spectroscopy and linear dichroism. The nanotubes are solubilised by aqueous sodium dodecyl sulfate, in which the nucleic acids also dissolve. The linear dichroism (LD) of the nanotubes, when subtracted from that due to the nanotubes/nucleic acid samples, gives the LD of the bound nucleic acid. The binding of the single-stranded DNA to the single-walled nanotubes is quite different from that previously observed for double-stranded DNA. It is likely that the nucleic acid bases lie flat on the nanotube surface with the backbone wrapping round the nanotube at an oblique angle in the region of 45 degrees . The net effect is like beads on a string. The base orientation with the single-stranded PNA is inverted with respect to that of the single-stranded DNA, as shown by their oppositely signed LD signals. 相似文献
79.
Teh-Chang Chou Holger Lange Rolf Gleiter Tibor Ggh Miroslav Krí Max H. Pfenninger Marian Valentíny Camille Ganter 《Helvetica chimica acta》1995,78(8):2011-2025
Three 1,4-dimethylidenecyclohexanes, bridged in the 2,6- and 3,5-positions by two ethano ( 4 ), one ethano and one propano ( 5 ), and two propano bridges ( 6 ) have been synthesized. The interaction of the two exocyclic methylidene groups has been investigated by He(I) photoelectron (PE) spectroscopy. It revealed a slightly larger energy difference (0.8 eV) for 4 and 5 as compared to the parent 1,4-dimethylidenecyclohexane ( 7 ) (0.7 eV). The interpretation of the PE spectra was based on the comparison with PE data of related systems and with the results of semiempirical calculations on 4–6 . 相似文献
80.
Upper-critical-solution-temperature (UCST) behavior in a ternary blend of poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl
styrene), and polystyrene is reported. The as-cast ternary blend is immiscible at ambient conditions and comprises two different
phases, and, however, turns into a miscible system above the “clarity point” ranging from 160 to 300 °C for different ternary
compositions. The maximum clarity point is labeled as the UCST for the ternary system, which is about 295 °C. Above the clarity
point, the originally immiscible ternary blend turned into one miscible phase. Owing to the thermodynamic UCST behavior and
kinetic hindrance, the immiscible ternary polymer blend can be locked into a pseudo-miscible state if it is heated to a temperature
above the clarity point followed by a rapid-cooling processing scheme. The quenched ternary blend can remain in a pseudo-miscible
state as long as the service temperature does not exceed the glass-transition temperature of the blend.
Received: 17 July 2001 Accepted: 3 October 2001 相似文献