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1.
The one-step synthesis of amino-polyether tri-tert-butyl ester monomer 2, by condensation of TRIS with tert-butyl acrylate, is reported. The nitrogen of the monomer can be protected with a Cbz group; subsequent removal of the tert-butyl esters with formic acid affords a triacid that is coupled to three monomers to afford an orthogonally protected two-generation, trifurcated polyether-polyamide dendron. The Cbz protecting group may be removed from the second-generation dendron without disturbing the tert-butyl esters of the periphery. 相似文献
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Chemosensors for the marine toxin saxitoxin 总被引:1,自引:0,他引:1
Gawley RE Pinet S Cardona CM Datta PK Ren T Guida WC Nydick J Leblanc RM 《Journal of the American Chemical Society》2002,124(45):13448-13453
Eleven anthracylmethyl crown ethers have been synthesized and evaluated as fluorescence sensors for the marine toxin saxitoxin. Fluorescence enhancement data are consistent with a 1:1 binding complex for all crowns. The binding constants are in the range of 10(4) M(-)(1) in ammonium phosphate buffer (pH 7.1) in 80% ethanol solvent. Selectivity for sensing saxitoxin versus several organic analytes has been demonstrated for the first time. Possible modes of binding are presented, and relevance to saxitoxin monitoring programs are discussed. 相似文献
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In this paper we extend the plane blow-up results of Grundy& McLaughlin (1997) to the three-dimensional Navier-Stokes equations.Using a solution structure originally due to Lin we first providenumerical evidence for the existence of blow-up solutions on- < x, z < , 0 y 1 with boundary conditions on y = 0and y = 1 involving derivatives of the velocity components.The formulation enables us to consider plane and radial flowas special cases. Various features of the computations are isolatedand are used to construct a formal asymptotic solution closeto blow-up. We show that the numerical and asymptotic analysesprovide a mutually consistent global picture which supportsthe conclusion that, for the family of problems we considerhere, blow-up in fact can take place in three dimensions butat an inverse linear rate rather than the faster inverse squareof the plane case. 相似文献
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Ice nucleating-active Pseudomonas fluorescens F264C was fed to Colorado potato beetles to determine bacterial retentioin in the beetle gut and its effect on the cold hardiness of this insect pest. The bacrterium was present in beetles recovered after overwintering in the field, seven months after their exposure to P. fluorescens. Retention was evident not only in the detection of the P. fluorescens ice nucleating gene, inaW, in bacterial cultures from beetle guts but also in the elevated supercooling points of some treated beetles. 相似文献
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A unique application of the CuIPr N-heterocyclic carbene (NHC) to the dehydrogenative self-coupling of diphenylsilane has been discovered. This transformation is carried out open to air at room temperature, yielding octaphenylcyclotetra(siloxane) quantitatively in 1 h. This preparation constitutes a significant improvement over existing methods for the preparation of this compound and demonstrates a novel mode of reactivity for CuIPr. The diphenylsilanone tetramer is the precursor to a number of industrially significant polymers. 相似文献
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Functionalized γ,δ-unsaturated oximes, constructed by regiospecific alkylation of appropriate oximes, may be rearranged and cyclized to Δ1-pyrrolines in good yield. 相似文献
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N-Methyl trans-fused perhydroisoindolines substituted with a tributylstannyl group in the 2-position have been prepared and used as precursors of the corresponding alpha-aminoorganolithiums. The steric course of the reactions of these and other conformationally rigid organolithiums with various electrophiles is summarized and compared with the steric course of the unsubstituted analogs. A mechanistic rationale for the steric course of electrophilic substitutions of these organolithiums is discussed. Pathways involving both polar electrophilic substitutions and radical couplings were observed with different electrophiles. 相似文献
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HARUN REŞIT YAZAR 《Pramana》2013,81(4):579-585
The sd-interacting boson approximation (sd-IBA) and the df-interacting boson approximation (df-IBA) can be related to each other and the states of the interacting boson approximation model can be identified with the fully symmetric states in the sdf interacting boson approximation model. A systematic study of the sdf-IBA model showed that the constructed Hamiltonian can successfully describe the strong octupole correlations in the deformed nuclei. We showed that the interacting boson approximation may account for many of these K π ?=?0+ states. It was found that the calculated energy spectra of the gadolinium isotopes agree quite well with the experimental data. The observed B(E2) values were also calculated and compared with the experimental data. 相似文献
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An efficient method for the synthesis of 2-alkyl- and 2-aryl pyrrolidines, piperidines, and azepanes from lactams, in either racemic or enantiopure form, is presented. The lactam nitrogens are acylated with either Boc anhydride or trans-cumylcyclohexyl (TCC) chloroformate. Selective reduction of the lactam carbonyl to the carbinolamide is followed by treatment with benzotriazole. Substitution of the benzotriazole is accomplished by treatment with organometallics, yielding the 2-substituted heterocycles. With TCC, up to 90% diastereoselectivity is achieved. After diastereomer purification, reductive removal of the auxiliary affords enantiopure 2-substituted heterocycles. A mechanistic hypothesis is presented that details the conformational equilibria of the key step. 相似文献