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Synthetic Access (synthetic + access)
Selected AbstractsSuzuki,Miyaura Coupling Reaction of Boronic Acids and Ethyl Glyoxylate: Synthetic Access to Mandelate DerivativesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 34 2008Irene Notar Francesco Abstract The palladium-catalyzed coupling reaction of arylboronicacids with ethyl glyoxylate provides a straightforward method for the synthesis of mandelic esters. Pd2(dba)3·CHCl3 in combination with 2-di- tert -butylphosphanylbiphenyl as the catalytic system and Cs2CO3 as the base were used. The reaction tolerates a wide range of functionalized boronicacids. Mandelic esters were isolated in good-to-excellent yields with a variety of neutral, slightly electron-rich, and slightly electron-poor substituents.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] ChemInform Abstract: Synthetic Access to Poly-Substituted 6-Alkoxyindoles from 1,3-Cyclohexanediones and Nitroolefins Through Facile Aromatization Reaction.CHEMINFORM, Issue 18 2010Li-Jian Ma Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Suzuki,Miyaura Coupling Reaction of Boronic Acids and Ethyl Glyoxylate: Synthetic Access to Mandelate Derivatives.CHEMINFORM, Issue 11 2009Irene Notar Francesco Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthetic Access to New Pyridone Derivatives Through the Alkylation Reactions of Hydroxypyridines with Epoxides.CHEMINFORM, Issue 11 2008Ahmet Kocak Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A New Synthetic Access to 2-Trihalogenomethyl-3,4-dihydrofuro[2,3-d]pyrimidin-4-ones.CHEMINFORM, Issue 14 2003Mykhaylo V. Vovk Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthetic Access to 5,10-Disubstituted Porphyrins.CHEMINFORM, Issue 12 2003Sabine Hatscher Abstract For Abstract see ChemInform Abstract in Full Text. [source] Asymmetric Synthetic Access to the Hetisine Alkaloids: Total Synthesis of (+)-NominineCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008Kevin Abstract A dual cycloaddition strategy for the synthesis of the hetisine alkaloids has been developed, illustrated by a concise asymmetric total synthesis of (+)-nominine (7). The approach relies on an early-stage intramolecular 1,3-dipolar cycloaddition of a 4-oxido-isoquinolinium betaine dipole with an ene,nitrile dipolarophile. Subsequent late-stage pyrrolidine-induced dienamine isomerization/Diels,Alder cascade allows for rapid construction of the carbonnitrogen polycyclic skeleton within this class of C20 -diterpenoid alkaloids. [source] Chemical synthesis and biotinylation of the thrombospondin domain TSR2PROTEIN SCIENCE, Issue 5 2009Theresa K. Tiefenbrunn Abstract The type 1 repeat domain from thrombospondin has potent antiangiogenic activity and a structurally interesting fold, making it an attractive target for protein engineering. Chemical synthesis is an attractive approach for studying protein domains because it enables the use of unnatural amino acids for site-specific labeling and detailed structure-function analysis. Here, we demonstrate the first total chemical synthesis of the thrombospondin type 1 repeat domain by native chemical ligation. In addition to the natural domain, five sites for side chain modification were evaluated and two were found to be compatible with oxidative folding. Several challenges were encountered during peptide synthesis due to the functional complexity of the domain. These challenges were overcome by the use of new solid supports, scavengers, and the testing of multiple ligation sites. We also describe an unusual sequence-specific protecting group migration observed during cleavage resulting in +90 Da and +194 Da adducts. Synthetic access to this domain enables the synthesis of a number of variants that can be used to further our understanding of the biochemical interaction network of thrombospondin and provide insight into the structure and function of this important antitumorogenic protein domain. [source] Vinyl-Pyridinium Triphenylamines: Novel Far-Red Emitters with High Photostability and Two-Photon Absorption Properties for Staining DNACHEMBIOCHEM, Issue 4 2007Clémence Allain Dr. Abstract A series of mono-, bis- and trisvinyl-pyridinium triphenylamines (TP-py) has been synthesised and evaluated for its one- and two-photon absorption (2PA) induced-fluorescence properties under biological conditions. Interestingly, these compounds are only weakly fluorescent in water, whereas their fluorescence emissions are strongly restored (exaltation factors of 20,100) upon binding to double-stranded DNA. Additional measurements in glycerol indicate that the fluorescence increases are the result of immobilisation of the dyes in the DNA matrix, which inhibits rotational de-excitation modes. This particular feature is especially remarkable in the case of the bis and tris derivatives (TP-2,py, TP-3,py), which each display a high affinity (Kd ,,M) for dsDNA. TPIF measurements have shown that TP-2,py and TP-3,py each have a large 2PA cross section (, up to 700 GM) both in glycerol and in the presence of DNA, which ranks them amongst the best 2PA biological fluorophores. Finally, one- and two-photon confocal imaging in cells revealed that these compounds perform red staining (,em=660,680 nm) of nuclear DNA with excellent contrast. The remarkable optical properties of the TP-py series, combined with their high photostability and their easy synthetic access, make these compounds extremely attractive for use in confocal and 2PA microscopy. [source] 9,10-Diarylanthracenes as Molecular Switches: Syntheses, Properties, Isomerisations and Their Reactions with Singlet OxygenCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2008Daniel Zehm Abstract A series of 9,10-diarylanthracenes with various substituents at the ortho positions have been synthesised by palladium-catalysed cross-coupling reactions. Such compounds exhibit interesting physical properties and can be applied as molecular switches. Despite the high steric demand of the substituents, products were formed in moderate-to-good yields. In some cases, microwave conditions further improved yields. Bis-coupling afforded two isomers (syn and anti) that do not interconvert at room temperature. These products were easily separated and their relative stereochemistries were unequivocally assigned by NMR spectroscopy and X-ray analysis. The syn and anti isomers exhibit different physical properties (e.g., melting points and solubilities) and interconversion by rotation around the aryl,aryl axis commences at <100,°C for fluoro-substituted diarylanthracenes and at >300,°C for alkyl- or alkoxy-substituted diarylanthracenes. The reactions with singlet oxygen were studied separately and revealed different reactivities and reaction pathways. The yields and reactivities depend on the size and electronic nature of the substituents. The anti isomers form the same 9,10-endoperoxides as the syn species, occasionally accompanied by unexpected 1,4-endoperoxides as byproducts. Thermolysis of the endoperoxides exclusively yielded the syn isomers. The interesting rotation around the aryl,aryl axis allows the application of 9,10-diarylanthracenes as molecular switches, which are triggered by light and air under mild conditions. Finally, the oxygenation and thermolysis sequence provides a simple, synthetic access to a single stereoisomer (syn) from an unselective coupling step. [source] TMC-95A Analogues with Endocyclic Biphenyl Ether Group as Proteasome InhibitorsCHEMISTRY & BIODIVERSITY, Issue 1 2004Markus Kaiser TMC-95A, a cyclic tripeptide metabolite of Apiospora montagnei, is a potent competitive inhibitor of proteasome. Based on the X-ray structure of its complex with yeast proteasome, the synthetically challenging structure of this natural product was simplified in a first generation of analogues by replacing the highly oxidized side-chain biaryl system with a phenyl-oxindole group. In the present study, the TMC-95 biaryl group was substituted with a biphenyl ether with retainment of significant proteasome inhibition. Because of the facile synthetic access of tripeptides containing in i, i+2 positions residues of the isodityrosine type, this new generation of TMC-95 analogues may represent promising lead structures for further optimization of affinity and selectivity of proteasome inhibitors. [source] | ||||||||||