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61.
62.
A novel bis(beta-cyclodextrin) was synthesized, and its binding behavior with steroids was investigated to demonstrate that the cooperative co-inclusion of guest and tether by two cyclodextrin moieties is operative to afford the highest molecular selectivity of up to 3.6 for deoxycholate over taurocholate. 相似文献
63.
The stereocontrolled synthesis of oligodeoxyribonucleoside phosphorothioates (PS-ODNs) using nucleoside 3'-O-oxazaphospholidine derivatives as monomer units is described. 2-Chloro-1,3,2-oxazaphospholidine derivatives were prepared from six kinds of enantiopure 1,2-amino alcohols and used for the phosphitylation reactions of 5'-O-protected nucleosides. A detailed study of these reactions revealed that the diastereoselectivity of the reaction depended on the structure of the enantiopure 1,2-amino alcohol, the reaction temperature, and the amine used as a scavenger of HCl. In addition, ab initio molecular orbital calculations for the 2-chlorooxazaphospholidine derivatives were carried out to elucidate the mechanism of these diastereoselective phosphitylation reactions. The LUMO of the 2-chloro-5-phenyloxazaphospholidine derivatives on the phosphorus atom was found to be almost orthogonal to the P-Cl bond. This LUMO may be involved in the phosphitylation reactions with predominant retention of the P-configuration. A series of dialkyl(cyanomethyl)ammonium salts were developed and used as activators for the condensation reactions of the diastereopure nucleoside 3'-O-oxazaphospholidines with 3'-O-protected nucleosides. In the presence of the new activators, the reactions proceeded rapidly to give the corresponding dinucleoside phosphite triesters. The diastereoselectivity of the condensation reaction did not depend on the counteranion but on the structure of the dialkyl(cyanomethyl)amine. In the presence of the activator, which consists of a relatively small dialkyl(cyanomethyl)amine, the condensation proceeded with excellent diastereoselectivity. After sulfurization and deprotection, diastereopure (R(p))- and (S(p))-dinucleoside phosphorothioates were obtained in excellent yields. The present methodology was also applied to the solid-phase synthesis of stereoregulated PS-ODNs. all-(R(p))-[T(PS)](3)T, all-(S(p))-[T(PS)](3)T, all-(R(p))-d[G(PS)A(PS)C(PS)]T, and all-(R(p))-[T(PS)](9)T were synthesized on a highly cross-linked polystyrene resin. 相似文献
64.
When milled together with bismuth shot in the presence of allyl halide, aromatic aldehydes readily underwent a Barbier-type allylation to afford the corresponding homoallyl alcohols in good yield. In contrast to the failure in solution reaction, aromatic ketones also underwent allylic carbonyl addition under solvent-free conditions to give the expected tertiary homoallyl alcohols in moderate to good yield. 相似文献
65.
Masaharu Ueno Satoshi D. Ohmura Makoto Wada Norikazu Miyoshi 《Tetrahedron letters》2019,60(7):570-573
We developed an environmentally friendly method for aerobic oxidation of alcohols using a commercially available, relatively benign bismuth salt as a catalyst. We found that the catalytic combination of BiBr3 with nitric acid is key for enhancing the reactivity. The reaction proceeds well under air, making the use of pure oxygen unnecessary. Each of the primary or secondary alcohols tested was oxidized to the corresponding aldehydes or ketones using this protocol. 相似文献
66.
Zhaoma Shu Iku Tanaka Azumi Ota Daichi Fushihara Naoko Abe Saki Kawaguchi Kosuke Nakamoto Fumiaki Tomoike Seiichi Tada Yoshihiro Ito Yasuaki Kimura Hiroshi Abe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6683-6687
Development of intracellular delivery methods for antisense DNA and siRNA is important. Previously reported methods using liposomes or receptor‐ligands take several hours or more to deliver oligonucleotides to the cytoplasm due to their retention in endosomes. Oligonucleotides modified with low molecular weight disulfide units at a terminus reach the cytoplasm 10 minutes after administration to cultured cells. This rapid cytoplasmic internalization of disulfide‐modified oligonucleotides suggests the existence of an uptake pathway other than endocytosis. Mechanistic analysis revealed that the modified oligonucleotides are efficiently internalized into the cytoplasm through disulfide exchange reactions with the thiol groups on the cellular surface. This approach solves several critical problems with the currently available methods for enhancing cellular uptake of oligonucleotides and may be an effective approach in the medicinal application of antisense DNA and siRNA. 相似文献
67.
Kondo T Kaneko Y Taguchi Y Nakamura A Okada T Shiotsuki M Ura Y Wada K Mitsudo TA 《Journal of the American Chemical Society》2002,124(24):6824-6825
Pyranopyrandiones were prepared by a novel ruthenium-catalyzed carbonylative dimerization of cyclopropenones via C-C bond cleavage. For example, treatment of dipropylcyclopropenone with a catalytic amount of Ru3(CO)12 and NEt3 in THF under 15 atm of carbon monoxide at 140 degrees C for 20 h gave a novel functional monomer, 3,4,7,8-tetrapropylpyrano[6,5-e]pyran-2,6-dione, in an isolated yield of 81%. Unsymmetrically substituted pyranopyrandiones were also obtained by ruthenium-catalyzed carbonylative coupling of cyclopropenones with alkynes under similar reaction conditions. 相似文献
68.
Imai M Tanaka M Tanaka K Yamamoto Y Imai-Ogata N Shimowatari M Nagumo S Kawahara N Suemune H 《The Journal of organic chemistry》2004,69(4):1144-1150
Intermolecular hydroacylation between salicylaldehydes 1, 26-40 and 1,4-penta- or 1,5-hexadienes 4-13 by Rh-catalyst proceeded under mild reaction conditions to give a mixture of iso- and normal-hydroacylated products 14-25, 41-55, and 57-60. In the hydroacylation reaction, chelation of both salicylaldehyde and diene to the Rh-complex plays a crucial role. The ratio of iso- and normal-hydroacylated products could be regulated by the addition of salicylic acid or amines. The effects of various Rh-complexes, solvents, and additives were examined, and the plausible mechanisms of the catalytic cycle were proposed on the basis of the deuterium-labeling salicylaldehyde experiments. 相似文献
69.
Nishiyama Y Kaneda M Saito R Mori T Wada T Inoue Y 《Journal of the American Chemical Society》2004,126(21):6568-6569
In the enantiodifferentiating photoaddition of ROH (R = Me, Et, i-Pr) to 1,1-diphenylpropene sensitized by fructosyl 1,4-naphthalenedicarboxylate in supercritical carbon dioxide, the enantiomeric excess of photoadduct increased with increasing bulkiness of the alcohol at all pressures used, with an accompanying sudden jump at the critical density, for which the enhanced clustering of alcohol, particularly in the subcritical pressure region, was revealed to be responsible from the fluorescence spectral examinations. 相似文献
70.
Kiyoharu Tadanaga Akira Miyata Daisuke Ando Naoko Yamaguchi Masahiro Tatsumisago 《Journal of Sol-Gel Science and Technology》2012,62(1):111-116
Using hot water treatment of sol–gel derived precursor gel films, Co–Al and Ni–Al layered double hydroxide (LDH) thin films
were prepared. The precursor gel films of Al2O3–CoO or Al2O3–NiO were prepared from cobalt or nickel nitrates and aluminum tri-sec-butoxide using the sol–gel method. Then, the precursor gel films were immersed in a NaOH aqueous solution of 100 °C. Nanocrystallites
of Co–Al and Ni–Al LDH were precipitated with the hot water treatment with NaOH solution. The largest amounts of nanocrystals
were obtained with a solution of pH = 10 for Co–Al LDH, and with that of pH = 9 for Ni–Al LDH. X-ray diffraction measurements
confirmed that this process formed CO3
2− intercalated LDHs. Both Co–Al and Ni–Al LDH thin films were confirmed to work as electrodes for electrochemical devices by
cyclic voltammogram measurements. 相似文献