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21.
Photocycloadditlon of (+)-isoplperltenone and cyclobutene-1-carboxylic acid gives an adduct which upon reduction with NaCNBH3 followed by thermolysis yields an isomer of isoaristolactone in an overall yield of 26%. 相似文献
22.
A norm on a group G is a function N mapping G into the set ofnon-negative real numbers such that for each x and y in G, N(xy1) N(x)+N(y) and N(e) = 0, where e is the identity element ofG. It is shown here that if F(X) is the free topological groupon any completely regular Hausdorff space X and H is a subgroupof F(X) generated by a finite subset of X, then any norm onH can be extended to a continuous norm on F(X). 相似文献
23.
Olefin cross-metathesis (CM) is potentially an attractive method for generating dynamic combinatorial libraries (DCLs). In order for the CM reaction to be useful for DCL production, the course of the reaction and product distribution must be relatively insensitive to functionality remote from the reacting centers. We report on the CM of a series of allyl- and homoallylamides that are strongly dependent on remote functionality. This includes an unusual example of a cis-selective CM. [Reaction: see text] 相似文献
24.
A chemical inhibitor reveals the role of Raf kinase inhibitor protein in cell migration 总被引:7,自引:0,他引:7
Raf kinase inhibitor protein (RKIP) is a modulator of cell signaling that functions as an endogenous inhibitor of multiple kinases. We demonstrate here a positive role for RKIP in the regulation of cell locomotion. We discovered that RKIP is the relevant cellular target of locostatin, a cell migration inhibitor. Locostatin abrogates RKIP's ability to bind and inhibit Raf-1 kinase, and it acts by disrupting a protein-protein interaction, an uncommon mode of action for a small molecule. Small interfering RNA-mediated silencing of RKIP expression also reduces cell migration rate. Overexpression of RKIP converts epithelial cells to a highly migratory fibroblast-like phenotype, with dramatic reduction in the sensitivity of cells to locostatin. RKIP is therefore the compound's valid target and a key regulator of cell motility. 相似文献
25.
Kevin J. Finn 《Tetrahedron》2006,62(31):7471-7476
Dibromobenzenes (o-, m-, and p-isomers) were converted to the corresponding cis-cyclohexadiene diols by whole-cell fermentation with Escherichia coli JM 109 (pDTG601A), an organism over-expressing the enzyme toluene dioxygenase (TDO). Absolute stereochemistry of new metabolites was determined, and (−)-conduritol was synthesized. 相似文献
26.
Reaction of the cationic complex [WI(CO)(NCMe){Ph2P(CH2)PPh2}(η2-MeC2ME)][BF4] with an equimolar amount of MX (MX = NaCl, NaBr, NaI, KNO2, KNO3, NaNCS or KOH) in acetone at room temperature gave the neutral complex [WIX(CO){Ph2P(CH2)PPh2}(η2-MeC2Me)] (1–7) in good yield. Complexes 1–7 have been characterized by elemental analysis (C, H and N), IR and 1H NMR spectroscopy. 相似文献
27.
Juan M. Kok Kevin C. Lim Brian W. Skelton Allan H. White 《Journal of Cluster Science》2004,15(3):377-386
The structural characterizations of some copper(I) halide (CuX) adducts with norbornadiene (nbd) are recorded. CuCl : nbd (1:1)4 (a redetermination), (2:1)2(|), are systems both based around Cu4Cl4 cubane-type cluster arrays. CuBr : nbd (7:3)(|)( 0.5 MeOH), a complex polymer with 3-symmetry, is believed to be the complex previously described as an adduct of 2:1 stoichiometry. Attempts to obtain an iodide counterpart have resulted in the definition of an ephemeral adduct CuI : MeCN (3:2)(|). 0.5 C7H8 in which, remarkably, the nbd is uncoordinated; the complex is a polymer, related to the [AgX(quinoline)](|) (X = Cl, Br) saddle polymer. 相似文献
28.
Kevin E. Bassler Kazuo Sasaki Robert B. Griffiths 《Journal of statistical physics》1991,62(1-2):45-88
Certain features in Frenkel-Kontorova and other models of phases with a one-dimensional modulation can be analyzed by assuming parallel interfaces separating sets of lattice planes belonging to two different phases, and treating the free energy to create interfaces, as well as the interaction of two, three, or more interfaces, as phenomenological parameters. A strategy employed by Fisher and Szpilka for interacting defects can be extended to the case of interfaces, allowing a systematic study of the phase diagram by ignoring all interface interactions, and then successively taking into account pair, triple, and higher-order terms. The possible phase diagrams which can occur near the point where =0 include: various sorts of endpoints analogous to critical endpoints, an accumulation point of first-order transitions and triple points, and a self-similar structure which we call an upsilon point, which turns out to be an accumulation point of an infinite number of segments of first-order transition lines, each of which terminates in two upsilon points. 相似文献
29.
30.
Ifk
1 andk
2 are positive integers, the partitionP = (1,2,...,
n
) ofk
1+k
2 is said to be a Ramsey partition for the pairk
1,k
2 if for any sublistL ofP, either there is a sublist ofL which sums tok
1 or a sublist ofP –L which sums tok
2. Properties of Ramsey partitions are discussed. In particular it is shown that there is a unique Ramsey partition fork
1,k
2 having the smallest numbern of terms, and in this casen is one more than the sum of the quotients in the Euclidean algorithm fork
1 andk
2.An application of Ramsey partitions to the following fair division problem is also discussed: Suppose two persons are to divide a cake fairly in the ratiok
1k
2. This can be done trivially usingk
1+k
2-1 cuts. However, every Ramsey partition ofk
1+k
2 also yields a fair division algorithm. This method yields fewer cuts except whenk
1=1 andk
2=1, 2 or 4. 相似文献