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91.
[reaction: see text] The enantiomers of spiro[4.4]nonane-1,6-diol have been transformed by different reaction pathways into the two possible carbaspironucleoside epimers with natural C1' absolute stereochemistry. 相似文献
92.
Chiral domains have been prepared by evaporation of a two-dimensionally chiral molecule, naphtho[2,3-a]pyrene (NP), onto the hexagonal Au(111) surface in an ultrahigh vacuum environment. High-resolution UHV scanning tunneling microscopy (STM) showed that NP formed chiral domains consisting of only one 2D enantiomer rather than racemic two-dimensional unit cells. A structural model is proposed that agrees with the STM observations. Chiral pockets between adsorbed molecules may be useful for binding a specific enantiomer of a 3D chiral molecule. 相似文献
93.
Piña IC Gautschi JT Wang GY Sanders ML Schmitz FJ France D Cornell-Kennon S Sambucetti LC Remiszewski SW Perez LB Bair KW Crews P 《The Journal of organic chemistry》2003,68(10):3866-3873
Four novel bisulfide bromotyrosine derivatives, psammaplins E (9), F (10), G (11), and H (12), and two new bromotyrosine derivatives, psammaplins I (13) and J (14), were isolated from the sponge Pseudoceratina purpurea, along with known psammaplins A (4), B (6), C (7), and D (8) and bisaprasin (5). The structures of psammaplins E (9) and F (10), which each contain an oxalyl group rarely found in marine organisms, were determined by spectroscopic analysis. Compounds 4, 5, and 10 are potent histone deacetylase inhibitors and also show mild cytotoxicity. Furthermore, compounds 4, 5, and 11 are potent DNA methyltransferase inhibitors. The biogenetic pathway previously proposed for the psammaplins class is also revisited. 相似文献
94.
Let θ > 1 and let ϕ : [0,1] → ℂ be such that the two-sided series
converges for all x ∊ [0,1], (then necessarily φ(0) = φ(1) = 0).Suppose
Define
For different classes of functions φ we show that
À notre ami, Jean-Louis Nicolas2000 Mathematics Subject Classification: Primary—11B83, 11B99 相似文献
95.
Savajols H Korichi A Ward D Appelbe D Ball GC Beausang C Beck FA Byrski T Curien D Dagnall P de France G Disdier D Duchêne G Erturk S Finck C Flibotte S Gall B Galindo-Uribarri A Haas B Hackman G Janzen VP Kharraja B Lisle JC Merdinger JC Mullins SM Pilotte S Prévost D Radford DC Rauch V Rigollet C Smalley D Smith MB Stezowski O Styczen J Theisen C Twin PJ Vivien JP Waddington JC Zuber K Ragnarsson I 《Physical review letters》1996,76(24):4480-4483
96.
Two repellent particles are bound to occupy two among thek
n
+1 adjacent sites 0=x
0
(n)
<x
1
(n)
<...<x
kn
(n)
=1, sayx
q
(n)
,x
q+1
(n)
. Define the Hamiltonian
q
(n)
=–ln(x
q+1
(n)
–x
q
(n)
) and the partition function 相似文献
97.
Marcia B. France Allyn K. Milojevich Tracy A. Stitt Angela J. Kim 《Tetrahedron letters》2003,44(52):9287-9290
Copper(I) bis(oxazoline) species are among the most enantioselective cyclopropanation catalysts that have been reported, although these catalysts generally give low diastereoselectivities. We have observed greatly improved diastereoselectivities using (trimethylsilyl)diazomethane as the carbon source. We have also identified several bis(oxazoline) species that also give comparable or higher enantioselectivities with (trimethylsilyl)diazomethane compared to the more readily available ethyl diazoacetate. The application of this methodology to several olefins has been explored. 相似文献
98.
Joel Aponte‐Guzmán Dr. Lien H. Phun Marchello A. Cavitt J. Evans Taylor Jr. Jack C. Davy Prof. Dr. Stefan France 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10405-10409
An Al(OTf)3‐catalyzed intramolecular cascade ring‐opening benzannulation of 2,3‐dihydrofuran O,O‐ and N,O‐acetals is described. The cascade sequence involves the dihydrofuran ring‐opening by acetal hydrolysis, an intramolecular Prins‐type cyclization, and aromatization to generate an array of benzo‐fused (hetero)aromatic systems in up to 95 % yield. This method represents the first example of dihydrofuran acetal usage in benzannulation reactions. The approach provides excellent regiocontrol based on the choice of alkenes used to form the requisite dihydrofuran acetals. 相似文献
99.
100.
We consider a branching random walk with a random environment in time, in which the offspring distribution of a particle of generation n and the distribution of the displacements of its children depend on an environment indexed by the time n. The environment is supposed to be independent and identically distributed. For AR, let Zn(A) be the number of particles of generation n located in A. We show central limit theorems for the counting measure Zn(·) with appropriate normalization. 相似文献