Search results for "DISCOVERY"
showing 10 items of 4119 documents
Dienediolates of unsaturated carboxylic acids in synthesis. Aldehydes and ketones from alkyl halides, by ozonolysis of β,γ-unsaturated α-alkyl carbox…
1997
Abstract A convenient two-step procedure for a two carbon homologative conversion of alkyl halides into aldehydes and methyl ketones by α-alkylation of unsaturated carboxylic acids, followed by ozonolysis is developed and applied to the synthesis of ω-chloro aldehydes. Triethylamine is superior to dimethyl sulfide or triphenylphosphine for cleavage of the ozonides, except when aldol condensation side reactions require use of protic solvents and iodide salts. Cleavage of the ozonides by triethylamine is shown to occur mainly through a reductive process.
Combinatorial chemistry of -hairpins
2000
Combinatorial chemistry is expanding rapidly both in terms of chemistry development and application to the synthesis of compound libraries for lead discovery and optimization. Combinatorial technologies continue evolving and developing, in fact they are being used as basic research tools in different fields that include peptide/protein folding. This review examines the use of combinatorial chemistry in the design of peptides and protein domains that adopt beta-sheet conformations. In particular, the use of conformationally restricted peptide libraries has allowed the identification of linear peptides that are folded in a beta-hairpin structure in plain aqueous solutions.
Combinatorial synthesis of amino acid- and peptide-carbohydrate conjugates on solid phase
2004
Carbohydrates are useful polyfunctional scaffold molecules which allow the selective attachment of a number of different side chains. The combinatorial solid phase synthesis of diverse amino acid or peptide conjugates of a polyfunctional glucose scaffold based on a set of selectively removable and orthogonally stable protecting groups is described. The resulting carbohydrate-peptide hybrids constitute potential turn mimetics.
Straightforward synthesis of bioconjugatable azo dyes. Part 1: Black Hole Quencher-1 (BHQ-1) scaffold
2014
Abstract Azo dyes are currently used to quench the fluorescence of energy donors in bioassays through Forster resonance energy transfer (FRET) phenomenon. Common examples of such dark quenchers are DABCYL and the three members of Black Hole Quencher® (BHQ) family. Yet, only carboxylic acid and phosphoramidite derivatives of such azo dyes are presently commercially available. This Letter presents a straightforward synthesis method to novel bioconjugatable quenchers derived from BHQ-1 scaffold and equipped with a reactive group being either azido, terminal alkyne, or maleimide. The potential utility of the ‘clickable’ azido and thiol-reactive derivatives was notably demonstrated through the p…
Modified photobehavior of carboxylic acid derivatives induced by protonation
1987
Abstract A series of carboxylic acid derivatives 1–6 containing a second interacting function have been converted into the corresponding O -protonated species or acylium ions upon treatment with 96% sulfuric acid or oleum, respectively, at room temperature. The resulting stable cations have been spectroscopically characterized and submitted to irradiation. Cis-trans photoisomerization was observed in the ionic speciesderived from trans -crotonic, fumaric and maleic acids, and maleic anhydride. By contrast protonated crotonolactone 5a+ was found to be photostable. Finally, protonated α-bromobutyrolactone 6a+ was clean and efficiently dehydrohalogenated to 5a+ upon irradiation. Since the norm…
Quantitative Bestimmungen der Bluteiwei�e, speziell des Transferrins und des Haptoglobins, bei der Porphyria cutanea tarda
1964
Es wurden quantitative Bestimmungen des Transferrins, Haptoglobins und des Eisens an 10 Patienten mit Porphyria cutanea tarda durchgefuhrt. Dabei konnte eine statistisch gesicherte Verminderung des Transferrins und Erhohung des Eisenspiegels im Serum bei P.c.t.-Kranken gegenuber gesunden Kontrollpersonen festgestellt werden. Es liegt daher eine relativ gesattigte Eisenbindungskapazitat vor, deren Bedeutung fur die Pathogenese der P.c.t. diskutiert wird.
Protonation and rearrangement of the tricyclo[4.2.2.22,5]dodeca-3,7,9,11-tetraene scaffold
2006
The biplanemers 2a,b contain enol ether substructures, which permit facile protonations of the π electron system. The subsequent ether cleavage is characterized by rearrangements of the polycyclic scaffold of the carbenium ions or the electroneutral primary products. Apart from the expected products 3a and 5a, a series of unexpected ketones and diketones (4a′, 9b, 10b, 11b, and 12b) were obtained.
Zur C-17-Oxidation von Clavinalkaloiden mit primärer alkoholischer Hydroxylgruppe
1975
Die Oppenauer-Oxidation von 1 mit Cyclohexanon fuhrt zu dem Aldolkondensationsprodukt 4 und der Carbonsaure 3. Analog konnte Lysergsaure (8) in geringer Menge aus 6 gewonnen und im Reaktionsgemisch von 7 nachgewiesen werden. Damit wurden erstmals Clavinalkaloide mit primarer alkoholischer Hydroxylgruppe chemisch zu den entsprechenden Carbonsauren oxidiert. C-17-Oxidation of Clavine Alkaloids with a Primary Alcoholic Hydroxyl Group. 1 is converted by Oppenauer oxidation with cyclohexanone to the aldol condensation product 4 and to the carboxylic acid 3. Lysergic acid (8) was obtained in a small yield by the analogous reaction of 6 and was found in the reaction mixture of 7. Thus clavine alka…
Generation and transformation of the [3.3.1]propellane skeleton by thermal rearrangements
1994
Abstract In a sequence of unexpected thermal rearrangements the strained monocyclic alkyne 4 is transformed into the tricyclic system 5 which yields in a flash vacuum pyrolysis again a monocyclic compound 10 .
2020
The facile synthesis and detailed investigation of a class of highly potent protease inhibitors based on 1,4-naphthoquinones with a dipeptidic recognition motif (HN-l-Phe-l-Leu-OR) in the 2-position and an electron-withdrawing group (EWG) in the 3-position is presented. One of the compound representatives, namely the acid with EWG = CN and with R = H proved to be a highly potent rhodesain inhibitor with nanomolar affinity. The respective benzyl ester (R = Bn) was found to be hydrolyzed by the target enzyme itself yielding the free acid. Detailed kinetic and mass spectrometry studies revealed a reversible covalent binding mode. Theoretical calculations with different density functionals (DFT…