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111.
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Salvino JM Gerard B Ye HF Sauvagnat B Dolle RE 《Journal of combinatorial chemistry》2003,5(3):260-266
An efficient solid-phase synthesis of mono-N-substituted piperazines is presented. The key transformation involves a selective borane amide bond reduction in the presence of a carbamate resin linkage. This synthetic route takes advantage of the large diverse pool of commercially available carboxylic acids, acid chlorides, and sulfonyl chlorides. The solid-phase approach facilitates parallel processing by eliminating the need for column chromatography after each synthetic step. The N-monosubstituted piperazines were shown to react with polymeric activated tetrafluorophenol (TFP) reagents to generate arrays of amides and sulfonamides in good purity for biological testing. 相似文献
114.
Karim Boulabiar Gerard Buskes Melvin Henriksen 《Journal of Mathematical Analysis and Applications》2003,280(2):334-349
In J. Math. Anal. Appl. 12 (1995) 258–265, Araujo et al. proved that for any linear biseparating map from C(X) onto C(Y), where X and Y are completely regular, there exist ω in C(Y) and an homeomorphism h from the realcompactification vX of X onto vY, such that The compact version of this result was proved before by Jarosz in Bull. Canad. Math. Soc. 33 (1990) 139–144. In Contemp. Math., Vol. 253, 2000, pp. 125–144, Henriksen and Smith asked to what extent the result above can be generalized to a larger class of algebras. In the present paper, we give an answer to that question as follows. Let A and B be uniformly closed Φ-algebras. We first prove that every order bounded linear biseparating map from A onto B is automatically a weighted isomorphism, that is, there exist ω in B and a lattice and algebra isomorphism ψ between A and B such that We then assume that every universally σ-complete projection band in A is essentially one-dimensional. Under this extra condition and according to a result from Mem. Amer. Math. Soc. 143 (2000) 679 by Abramovich and Kitover, any linear biseparating map from A onto B is automatically order bounded and, by the above, a weighted isomorphism. It turns out that, indeed, the latter result is a generalization of the aforementioned theorem by Araujo et al. since we also prove that every universally σ-complete projection band in the uniformly closed Φ-algebra C(X) is essentially one-dimensional. 相似文献
(a)=ωψ(a) for all aA.
115.
116.
We introduce a class of function algebras, that we call unimodular,
and study Toeplitz operators on the Hardy spaces associated to representing
measures on these algebras.We show that our class of function algebras is very
extensive and that a number of important results for Toeplitz operators and
their associated C*-algebras extend to the very general setting we consider.
Submitted: July 1. 2001. 相似文献
117.
Let M be a simply connected Riemannian symmetric space, with at most one flat direction. We show that every Riemannian (or
unitary) vector bundle with parallel curvature over M is an associated vector bundle of a canonical principal bundle, with
the connection inherited from the principal bundle. The problem of finding Riemannian (or unitary) vector bundles with parallel
curvature then reduces to finding representations of the structure group of the canonical principal bundle. 相似文献
118.
[reaction: see text] To facilitate the access to unique models for biological processes, we examined six different synthetic routes to octi(p-phenylene) rods with lateral and terminal substituents R(L) and R(T). This systematic study allowed us to increase to overall yield for the synthesis of a new class of oligo(p-phenylene) ionophores about 20 times and to provide general insights into the practicability of synthetic routes to multiply substituted molecular rods. 相似文献
119.
Gerard A. van Albada Nora Veldman Anthony L. Spek Jan Reedijk 《Journal of chemical crystallography》2000,30(1):69-72
The title compound, catena-[bis(azido-N)-copper(II)-(bis(2-benzimidazolyl)butane), [Cu(C18H18N4)(N3)2]n, was obtained from the reaction of the ligand bis(2-benzimidazolyl)butane and Cu(N3)2. The x-ray crystal structure is reported. The compound crystallizes in the monoclinic space group P21/c with a = 8.2524(10), b = 12.765(5), c = 9.1125(15) Å, = 106.423(12)°, Z = 2. The Cu(II) ions are square-planar coordinated with trans-oriented end-on binding azido ligands. The structure is a polynuclear chain with the benzimidazole bridging at each end. In addition a N(ligand)-H···N(azido) H-bridge [N(ligand)···N(azido) = 2.994(7) Å] is present, resulting in a pseudo 2-dimensional lattice. The characteristic azido infrared vibrations are found at 2060 and 2077 cm–1 (as(N3)) and 1284 and 1297 cm–1 ((N3)). 相似文献
120.
Biosynthesis of sulfated glycopeptide antibiotics by using the sulfotransferase StaL 总被引:2,自引:0,他引:2
The unique glycopeptide antibiotic A47934, produced by Streptomyces toyocaensis, possesses a nonglycosylated heptapeptide core that is sulfated on the phenolic hydroxyl of the N-terminal 4-hydroxy-L-phenylglycine residue. Genetic and biochemical experiments confirmed that StaL is a sulfotransferase capable of sulfating the predicted crosslinked heptapeptide substrate to produce A47934 both in vivo and in vitro. Incubation of purified His(6)-StaL with various substrates in vitro revealed substrate specificity and yielded two sulfo-glycopeptide antibiotics: sulfo-teicoplanin aglycone and sulfo-teicoplanin. Quantification of the antibacterial activity of desulfo-A47934, A47934, teicoplanin, and sulfo-teicoplanin demonstrated that sulfation slightly increased the minimum inhibitory concentration. This unique modification by sulfation expands glycopeptide diversity with potential application for the development of new antibiotics. 相似文献