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31.
[reaction: see text]. We have previously described a diastereofacially selective 1,3-dipolar cycloaddition reaction of isomünchnones with vinyl ethers. While adapting this methodology for solid phase synthesis, we discovered a chemoselective and self-promoted linker aminolysis that provides liberated product in high purity, at a significantly enhanced rate. Herein we describe the implementation of a chiral auxiliary as a solid-phase linker, the detailed investigation of its unique aminolysis, and the utility of this cleavage within a chemical diversity format. 相似文献
32.
Francis Garnier Pierre Krausz Jacques-Emile Dubois 《Journal of organometallic chemistry》1979,170(2):195-201
The photoinduced metathesis [W(CO)6CCl4hν] of cis- and trans-RCH=CHMe gives 2-butene in a very high trans but low cis stereoselectivity. Propene behaves like a cis olefin. These results are consistent with the proposal of a dinuclear tungsten intermediate, which requires high steric constraints in the transalkylidenation step. 相似文献
33.
Francis D. de Kőrösy 《Mikrochimica acta》1989,97(1-2):25-29
Donor or acceptor compounds in apolar organic solvents become charged at a high-field strength electrode and are driven to a surrounding low-field strength electrode of opposite sign. At 10 kV per cm the solutions conduct 3–7 times better when the highly charged electrode is positive in donor solutions. The opposite situation occurs in acceptor solutions. 相似文献
34.
The reactions of organolithium reagents and Grignard reagents with optically active alkoxygermanes R3GeOR′ have been studied [R3GeOR′ = ()-i-PrPhNpGeOCH3, ()-i-PrPhNPGeOMen and ()-MePhNpGeOMen]. Saturated reagents (e.g. butyllithium) give retention of configuration at germanium whilst unsaturated reagents (e.g. allyl- or benzyllithium) lead to inversion. 相似文献
35.
36.
Efficient method for visualization and isolation of proteins resolved in polyacrylamide gels 总被引:3,自引:0,他引:3
R T Francis J R Davie M Sayre E Rocha F Ziemer G Riedel 《Journal of chromatography. A》1984,298(1):115-121
Polyacrylamide gel electrophoresis is a popular method used to purify proteins for reconstitution experiments, amino acid composition and sequence determinations. In this report we describe methods that will be of general use in the isolation and characterization of proteins and the benefits of substituting boric acid for glycine in the electrophoresis tray buffers. We also describe how proteins resolved in a variety of gel systems (including those containing sodium dodecyl sulfate) may be rapidly visualized with 8-anilino-1-naphthalene sulfonic acid and efficiently transferred to a second gel for two-dimensional gel analysis, or isolated by electroelution for subsequent characterization. 相似文献
37.
Francis Pochat 《Tetrahedron letters》1981,22(37):3595-3596
Ar-C(CN)=NN=C(CN)-Ar and Ar-C(CN)=NNHCO-Ar′, easily prepared from the bromoderivatives Ar-CBr(SEt)-CN, afford in good yields, by heating in a basic medium, 3,6-diaryl-5 hydroxy-1,2,4-triazines. 相似文献
38.
Pirrung MC Liu Y Deng L Halstead DK Li Z May JF Wedel M Austin DA Webster NJ 《Journal of the American Chemical Society》2005,127(13):4609-4624
The principle of methyl scanning is proposed for determination of the sites of interaction between biologically active small molecules and their macromolecular target(s). It involves the systematic preparation of a family of methylated derivatives of a compound and their biological testing. As a functional assay, the method can identify the regions of a molecule that are important (and unimportant) for biological activity against even unknown targets, and thus provides an excellent complement to structural biology. Methyl scanning was applied to demethylasterriquinone B1, a small-molecule mimetic of insulin. A new, optimal total synthesis of this natural product was developed that enables the family of methyl scan derivatives to be concisely prepared for evaluation in a cellular assay. The results of this experiment were used to design a biotin-demethylasterriquinone conjugate for use as an affinity reagent. This compound was prepared in tens of milligram quantities in a four-step synthesis. 相似文献
39.
A new protecting group has been developed for the exocyclic amino groups of nucleosides that occur in DNA. 3-Phenyl-[{N-(2-trimethylsilyl-ethoxycarbonyl)-2-amino}]-propanoic acid used as the protective agent. 相似文献
40.
Jockusch RA Kroemer RT Talbot FO Snoek LC Carçabal P Simons JP Havenith M Bakker JM Compagnon I Meijer G von Helden G 《Journal of the American Chemical Society》2004,126(18):5709-5714
The beta(1-->4) glycosidic linkage found in lactose is a prevalent structural motif in many carbohydrates and glycoconjugates. Using UV and IR ion-dip spectroscopies to probe benzyl lactoside isolated in the gas phase, we find that the disaccharide unit adopts only a single, rigid structure. Its fully resolved infrared ion-dip spectrum is in excellent agreement with that of the global minimum structure computed ab initio. This has glycosidic torsion angles of phi(H) (H1-C1-O-C4') approximately 180 degrees and psi(H) (C1-O-C4'-H4') approximately 0 degrees which correspond to a rotation of approximately 150 degrees about the glycosidic bond compared to the accepted solution-phase conformation. We discuss the biological implications of this discovery and the generality of the strategies employed in making it. 相似文献