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51.
Nelson ML Ismail MY McIntyre L Bhatia B Viski P Hawkins P Rennie G Andorsky D Messersmith D Stapleton K Dumornay J Sheahan P Verma AK Warchol T Levy SB 《The Journal of organic chemistry》2003,68(15):5838-5851
A diverse collection of tetracycline derivatives has been synthesized utilizing Heck, Suzuki, and other palladium-coupling reactions via tetracycline arenediazonium and iodoarene salts. Large numbers of tetracyclines are now possible via these reactions, including numerous upper periphery derivatives of doxycycline, minocycline, sancycline, and methacycline modified at positions C7, C9, and C6-C13 on the tetracycline naphthacene ring. Application of palladium-coupling reactions to the tetracyclines has yielded new tetracycline classes with differing structural attributes, greatly increasing the structural diversity of this family of antibiotics, one of the last of the early antibiotic families to be expanded by organic and medicinal chemistry. 相似文献
52.
Stanley A. Bajue Choy Lewis Karen Clarke Fitzgerald B. Bramwell Brian O. Patrick Carolyn Pratt Brock 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(6):m207-m211
The title complexes [μ‐(E)‐4,4′‐(ethene‐1,2‐diyl)dipyridine‐κ2N:N′]bis[halotris(4‐methylphenyl)tin(IV)], [Sn2(C7H7)6X2(C12H10N2)], where halo is chloro (X = Cl) and bromo (X = Br) are isostructural. In both crystals, the molecules lie on inversion centers, and there are voids of ca 80 Å3 that could, but apparently do not, accommodate water molecules. The corresponding iodo structure (X = I) is almost, but not quite, isostructural with the other two compounds; when Br is changed to I, the length of the c axis decreases by more than 1 Å and the voids are no longer large enough to accomodate any solvent molecule. The related complex [μ‐(E)‐4,4′‐(ethene‐1,2‐diyl)dipyridine‐κ2N:N′]bis[chlorotriphenyltin(IV)], [Sn2(C6H5)6Cl2(C12H10N2)], crystallizes in a related structure, but the molecules lie on general rather than on special positions. The molecular structures of the four complexes are similar, but the conformation of the phenyl derivative is approximately eclipsed rather than staggered. 相似文献
53.
Vijaykumar D Mao W Kirschbaum KS Katzenellenbogen JA 《The Journal of organic chemistry》2002,67(14):4904-4910
Two different synthetic routes were explored for the synthesis of fluoro furanyl norprogesterone (FFNP) 1, a high-affinity ligand for the progesterone receptor (PgR) that is being developed as a PET imaging agent for PgR-positive breast cancer. Both approaches proceed through a key intermediate, triol 5. The first approach, starting from keto-ketal 2, employed a dioxenyl group as a synthon for installing a corticosteroid side chain in keto-alcohol 4. The second approach, starting from propargylic acetate 12b, involved the application of a two-step method, a Pd(II)-catalyzed oxidative rearrangement followed by a base-catalyzed acetate rearrangement of the intermediate unsaturated acetate 13b, to generate the requisite corticosteroid side chain in keto-acetate 14b. This intermediate was further elaborated to the final product 1 via efficient dihydroxylation with potassium permangnate, furan acetalization with scandium triflate, and mesylation and fluorination reactions. The palladium-catalyzed route is considerably more efficient than the dioxene approach for the synthesis of key intermediate triol 5, and the scandium triflate-catalyzed acetalization, in particular, led to a considerable improvement in the overall yield of the endo furan acetal alcohol 16a. This route provides a major improvement in the overall yield of the final progestin target, FFNP 1. 相似文献
54.
Shi G Wu JT Li Y Geleziunas R Gallagher K Emm T Olah T Unger S 《Rapid communications in mass spectrometry : RCM》2002,16(11):1092-1099
55.
Karen V. Baker John M. Brown Neil A. Cooley Gareth D. Hughes Richard J. Taylor 《Journal of organometallic chemistry》1989,370(1-3):397-406
The palladium dibromide complexes of (S,R)-(1,1′-bis-diphenylphosphino)-2-ferrocencylthyldimethylamine and (S,R)-(1-diphenylphosphino)-2-ferrocenylethyldimethylamine have been reduced with dilithiocyclooctatetraene to form the corresponding Pd0 cyclooctatetraene complexes. Their reactions with E-4-methoxy-2′-bromophenylethene, and then benzylmagnesium chloride at −60 to −30°C, provide information on the structure of intermediates in asymmetric cross-coupling. 相似文献
56.
Gooding KB Higgs R Hodge B Stauffer E Heinz B McKnight K Phipps K Shapiro M Winkler M Ng WL Julian RK 《Journal of the American Society for Mass Spectrometry》2004,15(6):884-892
Approximately 300,000 compounds from selected libraries were screened against a subdomain of a hepatitis C viral (HCV) RNA using a high throughput flow injection mass spectrometry (FIA-MS) method with automated data storage and analysis. Samples contained 2 microM RNA target and 10 microM of each of up to ten ligands. Preliminary studies to optimize operational parameters used the binding of aminoglycosides to the A44 subdomain of bacterial RNA. Binding (confirmed by titration) and sensitivity were maximized within the constraints of the library and throughput. The mobile phase of 5 mM ammonium acetate in 50% isopropanol maintained the noncovalent complexes and provided good detection by electrospray mass spectrometry. Additionally, this composition maximized general solubility of the various classes of compounds including the oligonucleotide and organic library molecules. Cation adduction was insignificant in this screen although some solute and target dependent acetate adduction was observed. The ion trap mass spectrometer provided sufficient mass resolution to identify complexes of RNA with known components of the library. Converted mass spectral data (netCDF) were subjected to two types of statistical evaluation based on binding. The first algorithm identified noncovalent complexes that correlated with the molecular weights of the injected compounds. The second yielded the largest peak in the noncovalent complex region of the spectrum; this spectrum may or may not correlate with expected well components. Sixty-three compounds were confirmed to bind by more stringent secondary testing. Titrations, which were carried out with selected binding compounds, yielded a range of dissociation constants. Biological activity was observed for eleven confirmed binders. 相似文献
57.
Sonnenschein RN Farias JJ Tenney K Mooberry SL Lobkovsky E Clardy J Crews P 《Organic letters》2004,6(5):779-782
A reinvestigation of Auletta sp. yielded the novel compound milnamide C (3) plus the known compounds milnamide A (1), milnamide B (hemiasterlin) (2), jasplakinolide (5), and geodiamolides A (6), D (7), E (8), and G (9). The isolation work was guided by cytoskeletal bioactivity data. Compounds 2 and 3 were shown to cause microtubule depolymerization, and 6-9 were shown to cause microfilament disruption. This biological activity and the structural elucidation of 3, including X-ray analysis, are reported here. [structure: see text] 相似文献
58.
Mollet K Catak S Waroquier M Van Speybroeck V D'hooghe M De Kimpe N 《The Journal of organic chemistry》2011,76(20):8364-8375
The reactivity of 2-(2-mesyloxyethyl)azetidines, obtained through monochloroalane reduction and mesylation of the corresponding β-lactams, with regard to different nucleophiles was evaluated for the first time, resulting in the stereoselective preparation of a variety of new 4-acetoxy-, 4-hydroxy-, 4-bromo-, and 4-formyloxypiperidines. During these reactions, transient 1-azoniabicyclo[2.2.0]hexanes were prone to undergo an S(N)2-type ring opening to afford the final azaheterocycles, which was rationalized by means of a detailed computational analysis. This approach constitutes a convenient alternative for the known preparation of 3,4-disubstituted 5,5-dimethylpiperidines, providing an easy access to the 5,5-nor-dimethyl analogues as valuable templates in medicinal chemistry. Furthermore, cis-4-bromo-3-(phenoxy or benzyloxy)piperidines were elaborated into the piperidin-3-one framework via dehydrobromination followed by acid hydrolysis. 相似文献
59.
Corey T. Love Wojtek Dmowski Karen E. Swider-Lyons 《Journal of solid state chemistry》2011,184(9):2412-2419
We use electrochemistry, high-energy X-ray diffraction (XRD) with pair-distribution function analysis (PDF), and density functional theory (DFT) to study the instabilities of Li2CuO2 at varying state of charge. Rietveld refinement of XRD patterns revealed phase evolution from pure Li2CuO2 body-centered orthorhombic (Immm) space group to multiphase compositions after cycling. The PDF showed CuO4 square chains with varying packing during electrochemical cycling. Peaks in the G(r) at the Cu-O distance for delithiated, LiCuO2, showed CuO4 square chains with reduced ionic radius for Cu in the 3+ state. At full depth of discharge to 1.5 V, CuO was observed in fractions greater than the initial impurity level which strongly affects the reversibility of the lithiation reactions contributing to capacity loss. DFT calculations showed electron removal from Cu and O during delithiation of Li2CuO2. 相似文献
60.
Griffin K Montagne C Hoang CT Clarkson GJ Shipman M 《Organic & biomolecular chemistry》2012,10(5):1032-1039
2-Methyleneaziridines can be tethered to a variety of alkene or alkyne acceptors through the saturated carbon of the heterocyclic ring by application of a simple lithiation/alkylation sequence (8 examples, 31-59%). Treatment of the resultant alkene bearing substrates with BF(3)·OEt(2) leads to cis-octahydrocyclopenta[c]pyrroles in which up to four contiguous stereocentres are created in a diastereocontrolled manner after reductive work-up. Using an alkyne based substrate, a 2,4,5,6-tetrahydrocyclopenta[c]pyrrole is produced by rapid tautomerisation of the initially formed bisenamine. Evidence that these (3 + 2) 'cycloadditions' proceed in a stepwise manner via a 2-aminoallyl cation is presented. 相似文献