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121.
Starting from the natural neo-clerodane diterpenoid teubotrin (1) several neo-clerodane derivatives (3-7,9-11) have been obtained. The naturally occurring diterpenoid teuscordinon (12) has also been synthesized from teubotrin (1), showing thereby how some of these transformations can be useful for the synthesis of other natural neo-clerodane diterpenes. The latter are of interest due to their activity as insect antifeedants and other important biological properties. 相似文献
122.
Cathodic reduction of -azidocinnamic ester under aprotic conditions on Hg, Pt, or graphite electrodes can be directed to high yields of N,N-diacylated dehydroaminoacid derivates (f.i. addition of acetic anhydride) or to almost quantitative yields of -aminocinnamic ester in very pure form by careful addition of H+-donors. The dehydroamino compounds in turn can be further reduced to the corresponding saturated compounds by following H+-addition and changed electrolysis potential. Almost no dimerization occurs. 相似文献
123.
Hitoshi Shimizu Kazuki Shimizu Atsuko Sugita Tsuyoshi Yamauchi Kazumi Morikawa 《Tetrahedron letters》2004,45(42):7837-7841
Two 21-nor-22-oxa-1α,25-dihydroxyvitamin D3 derivatives have been synthesized in quest of a drug with lower calcemic activity than Maxacalcitol, 22-oxa-1α,25-dihydroxyvitamin D3, being used as antihyperparathyroidism and antipsoriatic drug. Of two 21-nor products obtained, the product carrying one carbon elongated side chain with diethylcarbinol moiety has been found to exhibit comparable differentiation-inducing activity to Maxacalcitol with much lower exhibition of calcemic activity. 相似文献
124.
Xue Yuan HU Xue Sen FAN Xin Ying ZHANG Gui Rong QU Yan Zhen LI School of Chemical Environmental Sciences Henan Key Laboratory for Environmental Pollution Control Henan Normal University Xinxiang Chongqing University of Medical Sciences Chongqing 《中国化学快报》2005,(7)
Construction of tetrahydropyran rings has attracted a great deal of interests in organic synthesis in recent years1, since tetrahydropyran moiety constitutes a structural unit in a number of natural products2. In addition, tetrahydropyran derivatives possess wide range of biological activities and pharmacological properties, such as anticancer activity3 and antihypersensitivity4. Many methods for the preparation of such compounds have already been developed5. Among them, condensation of α, β… 相似文献
125.
Calaminici P Jug K Köster AM Arbez-Gindre C Screttas CG 《Journal of computational chemistry》2002,23(2):291-297
This paper presents calculations of dipole moments (mu), static polarizabilities (alpha), and first hyperpolarizabilities (beta) of phosphonic acid stilbene derivatives calculated in the framework of density functional theory. These calculations were performed using a finite field approach implemented in the density functional program ALLCHEM and were of an all-electron type using local exchange-correlation functional and specially designed basis sets. The molecular structures have been fully optimized using the semiempirical program MSINDO. Some of the investigated stilbenes have been synthesized very recently while others are described for the first time. Donor and acceptor groups of these analogues have been modified and the influence of these changes on the first hyperpolarizabilities has been investigated. This work demonstrates that the nonlinear optical response beta of these compounds increases dramatically when the acceptor moiety is displaced by analogues containing alkali metal groups. A general mechanism for the design of novel nonlinear optical materials with large first hyperpolarizabilities is described. 相似文献
126.
L. H. C. Mattoso S. K. Manohar A. G. Macdiarmid A. J. Epstein 《Journal of polymer science. Part A, Polymer chemistry》1995,33(8):1227-1234
Syntheses of parent polyaniline and methyl, methoxy, and ethoxy ortho-substituted polyanilines were performed using the conventional chemical methodology and monitored using the new open-circuit-potential (Voc) profile technique. The intermediate pernigraniline oxidation state was identified and isolated at the Voc maximum (A) during the conventional chemical synthesis of poly(o-methoxyaniline) in the emeraldine oxidation state. The introduction of the substituent on the aniline ring leads to longer polymerization times and lower Voc values. Syntheses in the presence of two different monomers in solution were also investigated and showed preferential polymerization of the monomer with the lowest Voc potential. All polymers produced were characterized by elemental analysis, gel permeation chromatography, UV-VIS spectroscopy, and cyclic voltammetry. The influence of the substituent on the Voc profile and on the polymer characteristics are rationalized in terms of steric and electronic effects. © 1995 John Wiley & Sons, Inc. 相似文献
127.
Alexander D. Dilman Dmitry E. Arkhipov Valentine P. Ananikov Vladimir A. Tartakovsky 《Journal of organometallic chemistry》2005,690(16):3680-3689
A general method for the synthesis of carbon-centered tris(pentafluorophenyl)silyl derivatives (RSi(C6F5)3) by reaction of trichlorosilanes (RSiCl3) with pentafluorophenylmagnesium bromide was described. The crystal structures of obtained compounds were studied by X-ray diffraction analysis (7 structures). The peculiarities of crystal packing were analyzed by means of DFT calculations. 相似文献
128.
Summary The retention of 22 ring-substituted phenol derivatives on porous graphitized carbon (PGC) (eluents: acetonitrile — water and methanol — water mixtures) and on octadecylsilica (ODS) (eluents: methanol — 0.025 M KH2PO4 mixtures) was determined, and the relationship between retention and physicochemical parameters were evaluated by principal component analysis followed by two-dimensional nonlinear mapping and by cluster analysis as well as by canonical correlation analysis. Calculations proved that marked differences can be detected between the retention characteristics of PGC and ODS columns, and the electronic parameters of phenol derivatives have the highest impact on their retention. The comparison of various multivariate mathematical-statistical methods indicated that principal component analysis followed by two dimensional non-linear mapping is the most appropriate method for the evaluation of large data matrices in RP-HPLC. 相似文献
129.
Lemi Türker 《Journal of Molecular Structure》2004,680(1-3):47-51
Semiempirical quantum chemical calculations at the level of AM1 (restricted Hartree–Fock) have been performed on a fullerene derivative, C54N4, theoretically obtained from C60 and its mono and diprotonated forms. All these structures are stable, but endothermic in nature. Some calculated geometrical and physicochemical properties of these have also been reported. 相似文献
130.
Carola Griehl Dieter Ströhl Hans Jeschkeit Erich Kleinpeter 《Monatshefte für Chemie / Chemical Monthly》1992,123(6-7):647-654
Summary During the addition of amines to maleylamino acids in general -amino derivatives are formed. In order to change the reactivity within the vinylogous maleyl system we introduced the -benzylester group into the starting compound N-(cis--carboxyacryloyl)-phenylalanine methylester1. The obtained benzylester2 is adding benzylamine in -position yielding N-benzyl--aspartyl(-benzyl)-phenylalanine methylester4. The addition reaction was investigated by1H-NMR-spectroscopy. The structures of the compounds have been confirmed by elemental analysis, IR,1H-NMR and13C-NMR spectroscopy. 相似文献