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21.
Gilles Gosselin Jean Louis Imbach Leroy B. Townsend Raymond P. Panzica 《Journal of heterocyclic chemistry》1979,16(6):1185-1191
Ribosylation of the trimethylsilyl derivative ( 1b ) of imidazole-2-thione ( 1a ) using either stannic chloride or silver perchlorate as catalyst resulted in the formation of the acylated derivatives of 1-(β-D-ribofuranosyl)imidazole-2-thione ( 3c ) and 1,3-di-(β-D-ribofuranosyl)imidazole-2-thione ( 4c ) with the latter predominating ( 4c:3c , ca. 2:1 ). The diribosylated nucleoside 4c was shown to be the N,N-disubstituted product rather than the N,S-disubstituted product by 1H nmr and 13C nmr spectroscopy. Employment of the iodine-catalyzed fusion procedure reversed the aforementioned product ratios and provided the monoriboside 3c in excellent yield. When the trimethylsilyl derivative ( 5b ) of 2-methylthioimidazole ( 5a ) was reacted with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide ( 2d ) in acetonitrile, the major product was 1,3-di-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-imidazole-2-thione ( 4b ). The formation of 4b in this reaction is thought to arise via the Hilbert-Johnson mechanism. 相似文献
22.
Reaction of 2-aminoethanethiol ( 3 ) with trans-3-(p-methoxyplienyl)glycidate ( 4 ) gave the rac.-cis-1,4-thiazepinone 5 and a by-product 6 . The structure of 5 was proven by X-ray crystallography. The X-ray data revealed that this compound adopts the chair conformation in the solid state and the heterocyclic ring is sevenmembered. The structure of the by-product 6 was elucidated on the basis of spectral data. Compounds 9 and 10 were inactive as calcium channel blocking agents. 相似文献
23.
The palladium catalysed condensation of Grignard reagents with silyl derivatives of 8-bromopurine nucleosides and 8-bromoadenosine-3′,5′ cyclic monophosphate is a convenient method for the preparation of free 8-alkylpurine nucleosides and 8-alkyladenosine-3′,5′ cyclic monophosphate. 相似文献
24.
A trideaza analog of aminopterin, N-(4[2-(2,4-diamino-6-quinazolinyl)ethyl]benzoyl)-L-glutamic acid, was prepared by a Wittig condensation of 2,4-diaminoquinazoline-6-carboxaldehyde and [P-(N-[1,3-bis(ethoxycarbonyl)propan-1-yl]aminocarbonyl)phenylmethyl]triphenylphosphonium bromide followed by catalytic reduction and mild hydrolysis. This compound was found to have confirmed inhibitory activity against leukemia L1210 in mice. 相似文献
25.
Hegedus LS Geisler L Riches AG Salman SS Umbricht G 《The Journal of organic chemistry》2002,67(22):7649-7655
Butenolides 5a and 13 were used as optically active templates in the de novo synthesis of 4'-disubstituted nucleoside analogues. The butenolides were reduced and acylated in situ to give acetates 10 and 14. Vorbrüggen coupling gave the protected nucleoside analogues 11 and 15. Reduction of 11 gave 4'-ethoxy-2',3'-dideoxythymidine (6) and deprotection of 15 gave 4'-ethoxy-2',3'-dideoxydidehydrothymidine (7). The cis-dihydroxylation of a variety of butenolides occurred with the major product formed from oxidation of the beta-face. 相似文献
26.
Rosenthal SJ Tomlinson I Adkins EM Schroeter S Adams S Swafford L McBride J Wang Y DeFelice LJ Blakely RD 《Journal of the American Chemical Society》2002,124(17):4586-4594
To explore the potential for use of ligand-conjugated nanocrystals to target cell surface receptors, ion channels, and transporters, we explored the ability of serotonin-labeled CdSe nanocrystals (SNACs) to interact with antidepressant-sensitive, human and Drosophila serotonin transporters (hSERT, dSERT) expressed in HeLa and HEK-293 cells. Unlike unconjugated nanocrystals, SNACs were found to dose-dependently inhibit transport of radiolabeled serotonin by hSERT and dSERT, with an estimated half-maximal activity (EC(50)) of 33 (dSERT) and 99 microM (hSERT). When serotonin was conjugated to the nanocrystal through a linker arm (LSNACs), the EC(50) for hSERT was determined to be 115 microM. Electrophysiology measurements indicated that LSNACs did not elicit currents from the serotonin-3 (5HT(3)) receptor but did produce currents when exposed to the transporter, which are similar to those elicited by antagonists. Moreover, fluorescent LSNACs were found to label SERT-transfected cells but did not label either nontransfected cells or transfected cells coincubated with the high-affinity SERT antagonist paroxetine. These findings support further consideration of ligand-conjugated nanocrystals as versatile probes of membrane proteins in living cells. 相似文献
27.
Amino‐alcohol derivatives of fragrant, volatile aldehydes and ketones were synthesized in a one‐pot procedure by sequential cyanohydrin formation with trimethylsilyl cyanide and reduction with lithium aluminium hydride, or by ammonolysis of epoxide precursors. The amino alcohols are nonvolatile, stable properfumes releasing fragrant carbonyls by oxidation with sodium periodate or sodium bismuthate. Examples include amino alcohol properfumes of citronellal, Lilial®, lauryl aldehyde, menthone, benzaldehyde, and anisaldehyde. 相似文献
28.
Crowe MC Kapoor RN Cervantes-Lee F Párkányí L Schulte L Pannell KH Brodbelt JS 《Inorganic chemistry》2005,44(18):6415-6424
Electrospray ionization (ESI) quadrupole ion trap mass spectrometry (QIT-MS) and collisionally activated dissociation (CAD) were used to evaluate the rare-earth binding properties of two hydrophobic carbamoylmethylphosphine oxide (CMPO) ligands, the normal bidentate variety, (t-BuC6H4)2P(O)CH2C(O)N(i-Bu)2 (A), a new potentially tridentate extractant, (t-BuC6H4)2P(O)CH[CH2C(O)N(i-Bu)2]C(O)N(i-Bu)2 (B), and tributyl phosphate. The mass spectral results obtained from analysis of 1% HNO3/methanol solution containing the ligands and dissolved lanthanide salts reveal that the favorable stoichiometries of the ligand/metal/nitrate complexes are 2:1:2 for the bidentate ligand A, 1:1:2 for the tridentate ligand B, and 3:1:2 for the monodentate tributyl phosphate. These observed stoichiometries correlate with the number of available binding sites on each ligand as well as with potential steric effects. Energy-variable collisionally activated dissociation experiments showed that for the 2:1:2 complexes involving ligand A or B, as the ionic radius of the bound metal decreased, the removal of nitric acid required less energy and resulted in less extensive spontaneous solvent coordination. This experimental trend suggests that, as the ionic radius of the lanthanide ion decreases, a pair of the carbamoylmethylphosphine ligands is able to more completely solvate the bound metal ion thereby weakening the nitrate-metal interaction. 相似文献
29.
Cantat T Jaroschik F Nief F Ricard L Mézailles N Le Floch P 《Chemical communications (Cambridge, England)》2005,(41):5178-5180
New samarium carbene complexes have been synthesized and characterized by X-ray diffraction analysis; the carbenic nature was assessed by reactivity studies. 相似文献
30.
In designing an experimentin which non-linear regression analysis is used to evaluate the physicochemical parameters that chracterize the behavior of the system being studied, it would be useful to be able to predict how the number of data points affects th reliabilities of the values obtained. The relation between these depends on hos the points are distributed as well as on the nature of the equation to which thd data are fitted. Weighted non-linear regression analysis has been applied to six common equations involving a total of fourteen parameters, using a number of n of points that was varied from 4 to 相似文献