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101.
Lawrence L. Martin Susan J. Scott Linda L. Setescak Donna Van Engen 《Journal of heterocyclic chemistry》1987,24(6):1541-1549
1,2,3,4-Tetrahydrobenzo[c]-1,5-naphthyridine ( 5a ) was prepared by a novel synthetic route involving the rearrangement of (±)-(Z)-1,10a-dihydropyrrolo[1,2-b]isoquinoline-3,10(2H,5H)-dione oxime to afford 1,4-dihydrobenzo[c]-1,5-naphthyridin-2(3H)-one, which was reduced to 5a. The cholinomimetic activity observed with 5a prompted the synthesis and biological evaluation of additional analogues. 相似文献
102.
Experimental kinetic data coupled with kinetic modeling implicates a tetrameric transition state in the Soai autocatalytic alkylation of pyrimidyl aldehydes. The kinetic model accurately predicts both the reaction rate and the amplification in enantiomeric excess observed in reactions carried out under a wide range of conditions. These studies reveal the Soai reaction to be an example of true autocatalytic efficiency in a template-directed "minimal system" for self-replication. 相似文献
103.
104.
Toby M. Chapman Donna M. Rakiewicz-Nemeth John Swestock Ramazan Benrashid 《Journal of polymer science. Part A, Polymer chemistry》1990,28(6):1473-1482
Segmented polyurethanes with N-alkylated amides as soft blocks as prepared. Comparisons are made with both a poly(ester urethane) and a poly(ether urethane) with the same hard block; the poly(amide urethane) is more hydrolytically stable than the polyester containing material and demonstrates greater thermooxidative stability than that with the polyether moiety. The aliphatic poly(amide urethane)s remain transparent upon exposure to uv light. 相似文献
105.
Details of a novel radical-initiated polyolefinic cyclization approach to linear condensed cyclopentanoids are reported. The strategy is executed in three stages: (1) Sn2′-anti opening of a vinyl lactone to produce a trans-3,5-disubstituted cyclopentene, (2) rapid elaboration to a cyclization precursor, and (3) single step tandem radical cyclization to produce a cis-anticis tricyclo[3.3.0]undecane. Model substrates and give high yields of tricyclic products and , respectively. An effort to rationalize the interesting endo selectivity via the Beckwith transition state model is proposed. Cyclizations of and to and demonstrate the viability of a tandem hexenyl-hexynyl cyclization. The work culminates with a total synthesis of (±)hirsutene. A selective approach to methyl substituted vinyl lactones by Claisen rearrangement-phenylselenolactonization-elimination of acetoxy cyclopentenols is exemplified by the synthesis of . Tandem cyclization of produces hirsutene () in a single step. Alternatively, cyclization of yields trimethylsilyl hirsutene. 相似文献
106.
Hsinhsi Lai Daniel S. Jones Donna C. Schwind D. Paul Rillema 《Journal of chemical crystallography》1990,20(4):321-325
The X-ray structure determination of the complex tris(2,2-bipyrazine)ruthenium(II) hexafluorophosphate, [Ru(C8N4H6)3](PF6)2, has shown that the compound crystallizes in the monoclinic space group P21/c witha=13.459(5),b=23.486(8),c=17.913(10) Å,=139.85(1)°, andZ=4. Each asymmetric unit also contains one dimethylformamide and one water molecule. Least-squares refinement led to an R factor of 0.074 based on 3463 reflections for which I>2(I). The [Ru(C8N4H6)3]2+ cation has no crystallographic symmetry, but the requirements for point symmetry 32 are nearly met. The six Ru-N bond lengths agree within experimental error and have an average length of 2.05(1) Å. 相似文献
107.
Christian Jackson Donna J. Frater Jimmy W. Mays 《Journal of Polymer Science.Polymer Physics》1995,33(15):2159-2166
Six-arm star polystyrenes having varying numbers of short and long arms attached to the same molecule have been synthesized by anionic polymerization. The molecules have been characterized by high resolution size exclusion chromatography using multiangle light scattering and viscosity detectors. This technique has allowed the radii of gyration and intrinsic viscosities to be measured for stars with each possible combination of arms. The branching parameters g and g′ are computed and compared with theoretical expectations. It is found that short arms add preferentially to the stars, because of reduced steric effects. The molecule with one long and five short arms exhibits behavior closest to that of a linear chain (largest branching ratios). The effect of arm polydispersity on solution properties of stars is discussed. © 1995 John Wiley & Sons, Inc. 相似文献
108.
Donna Glassbrenner 《Proceedings of the American Mathematical Society》1996,124(2):345-353
We characterize strong F-regularity, a property associated with tight closure, in a large class of rings. A special case of our results is a workable criterion in complete intersection rings.
109.
110.
Miguel F. Braa María Jesús Prez de Vega Denise Perron Donna Conlon Peter F. Bousquet Simon P. Robinson 《Journal of heterocyclic chemistry》1997,34(3):807-812
The 6-substituted benzimidazo[1,2-c]quinazoline 1 is a lead structure from our DNA intercalator program and is cytotoxic to the human colon cancer tumor line HT-29 with an inhibitory concentration 50, IC50 of 4.00 μM. In order to try and improve the limited cytotoxicity of this class of compound we prepared a series consisting of two benzimidazo[1,2-c]quinazoline moieties linked by a polyalkylamino bridge, of different length and substitution. The compound with the -NH-(CH2)3-N(CH3)-(CH2)3-NH-bridge had an inhibitory concentration 50, IC50 of 0.5 μM. When tested in vivo, however, no clear anti-tumor activity was produced in the human breast cancer tumor line MX-1 or the human melanoma tumor line LOX, human tumor xenografts models. 相似文献