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991.
Johannes?Winkler Ernst?Urban Christian R.?NoeEmail author 《Monatshefte für Chemie / Chemical Monthly》2004,135(1):109-116
Summary. A synthesis of the amino sugar 2-amino-2,3-didesoxyribose is described. Starting from D-glucosamine, -methylfuranoside was obtained in eight steps in 20% yield. This carbohydrate is a novel building block for nucleosides and for backbone modified antisense oligonucleotides with 2–5 amide linkages. 相似文献
992.
Larsen J Rasmussen BS Hazell RG Skrydstrup T 《Chemical communications (Cambridge, England)》2004,(2):202-203
A disphosphine-palladium(0) complex capable of recognising barbiturates has been prepared. Oxidative addition studies with a barbitiurate:aryl iodide conjugate provided new Pd(ii) complexes where the positioning of the Pd-bound aryl group is controlled by the molecular recognition event. 相似文献
993.
Nielsen LP Stevenson CP Blackmond DG Jacobsen EN 《Journal of the American Chemical Society》2004,126(5):1360-1362
The mechanism of the hydrolytic kinetic resolution (HKR) of terminal epoxides was investigated by kinetic analysis using reaction calorimetry. The chiral (salen)Co-X complex (X = OAc, OTs, Cl) undergoes irreversible conversion to (salen)Co-OH during the course of the HKR and thus serves as both precatalyst and cocatalyst in a cooperative bimetallic catalytic mechanism. This insight led to the identification of more active catalysts for the HKR of synthetically useful terminal epoxides. 相似文献
994.
Jens Christoffers Thomas Werner Angelika Baro Peter Fischer 《Journal of organometallic chemistry》2004,689(22):3550-3555
A 3-tert-butyl-1-(stannylpropyl)-functionalized cyclopentadienyl ligand precursor 6 is readily available in 64% overall yield from allylic alcohol 1 by a three-step reaction sequence including Pd-catalyzed hydrostannylation with Ph3SnH. Treatment with FeCl2 and ZrCl4 · 2THF afforded corresponding ferrocene and zirconocene derivatives. Transmetallation of Sn-Ph with Li-Bu was observed under these reaction conditions by using BuLi as a base. 相似文献
995.
Linear nanotubular boron-carbon heterojunctions are systematically constructed and studied with the help of ab initio total energy calculations. The structural compatibility of the two classes of materials is shown, and a simple recipe that determines all types of stable linear junctions is illustrated in some detail. Our results also suggest the compatibility of various technologically interesting types of nanotubular materials, leading to different types of nanotubular compound materials, and pointing out the possibility of wiring nanotubular devices within heterogeneous nanotubular networks. 相似文献
996.
Eberhard Reimann Christian Ettmayr 《Monatshefte für Chemie / Chemical Monthly》2004,135(10):1289-1295
Summary. Strecker reaction of iodophenethylamines with phenylacetaldehydes afforded the corresponding -aminonitriles, which on treatment with i-propyl magnesium chloride underwent a Bruylants reaction to give the title compounds. Their structures were deduced by NMR and by an independent preparation starting from papaverine. The educts were easily available by standard procedures. 相似文献
997.
998.
Christian P Rajaraman G Harrison A Helliwell M McDouall JJ Raftery J Winpenny RE 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2550-2555
We report a carboxylate triangle consisting of three manganese(II) centres which is made from manganese(II) carbonate and pivalic acid. The magnetic exchange within the triangle is extremely weak, and antiferromagnetic. Several models have been used to fit the magnetic data, and the best fit uses two weak antiferromagnetic coupling constants of J(1)=-0.588 cm(-1) and J(2)=-0.855 cm(-1). Exchange interactions between the metal centres has been calculated using DFT adopting all the three possible Heisenberg models for a trinuclear system and the results are compared with experimental values. Spin density distribution is used to analyse the nature of the coupling between the metal centres. EPR spectroscopy has been used to explore the nature of the ground state. Recrystallisation of the trinuclear compound from MeCN gives a polymer, while oxidation in air leads to a known compound--an edge-sharing bitetrahedral (MnIII2MnII4) cage. 相似文献
999.
Phipps RK Petersen BO Christensen KB Duus JØ Frisvad JC Larsen TO 《Organic letters》2004,6(20):3441-3443
[structure: see text] Hesseltin A 1, a novel compound of mixed polyketide-terpenoid origins was isolated from the filamentous fungus Penicillium hesseltinei. The structure and stereochemistry were determined from extensive one- and two-dimensional NMR and mass spectral data. 相似文献
1000.
Ferenczi Valentin; Pelczar Anna Maria; Rosendal Christian 《Bulletin London Mathematical Society》2004,36(3):396-406
The following property of a normalized basis in a Banach spaceis considered: any normalized block sequence of the basis hasa subsequence equivalent to the basis. Under uniformity or othernatural assumptions, a basis with this property is equivalentto the unit vector basis of c0 or lp. An analogous problem concerningspreading models is also addressed. 2000 Mathematics SubjectClassification 46B20 (primary), 46B15 (secondary). 相似文献