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Synthetic Steps (synthetic + step)
Selected AbstractsSynthesis of [phenyl-2- 3H]-travoprost: isopropyl ester prodrug of a selective prostaglandin FP receptor agonistJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2001Robert Selliah Abstract A method for the preparation of tritium labeled travoprost, a new ocular hypotensive prostaglandin, is described. A highly selective catalytic deiodination has been identified which provides [phenyl-2- 3H]-travoprost in a single synthetic step from 2,-iodo-travoprost. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of Enantiopure Sulfonimidamides and Elucidation of Their Absolute Configuration by Comparison of Measured and Calculated CD Spectra and X-Ray Crystal Structure DeterminationCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2010Christin Worch Abstract Straightforward syntheses of enantiopure N -benzoyl- and N - tert -butyloxycarbonyl-protected sulfonimidamides, which can be used as building blocks in newly designed catalysts, are presented. Key synthetic step is a dynamic resolution of a racemic sulfinic acid sodium salt. All subsequent transformations proceed stereospecifically. The absolute configurations at the sulfur atoms of both sulfonimidamides were determined by comparison of measured and calculated CD spectra. An X-ray crystal structure determination of a sulfonimidoylguanidine derivative confirmed this result. [source] 2-Substituted Benzo[b]furans from (E)-1,2-Dichlorovinyl Ethers and Organoboron Reagents: Scope and Mechanistic Investigations into the One-Pot Suzuki Coupling/Direct Arylation,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010Laina M. Geary Abstract 2-Substituted benzo[b]furans can easily be assembled from simple phenols, boronic acids or other organoboron reagents, and trichloroethylene. The overall process requires only two synthetic steps, with the key step being a one-pot sequential Suzuki cross-coupling/direct arylation reaction. The method tolerates many useful functional groups and does not require the installation of any other activating functionality. The modular nature of the process permits the rapid synthesis of many analogues using essentially the same chemistry, of particular value in drug development. Results of kinetic isotope effect studies and investigations into the regioselectivity of the process indicate that the direct arylation step most likely does not involve an electrophilic palladation. The most likely mechanism lies somewhere on the continuum between a C,H bond metathesis and an assisted palladation or concerted metallation-deprotonation pathway. [source] Efficient Synthesis of ,-Glycosphingolipids by Reaction of Stannylceramides with Glycosyl Iodides Promoted by TBAI/AW 300 Molecular SievesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2009José Antonio Morales-Serna Abstract TBAI and acid-washed molecular sieves efficiently promoted the glycosylation of stannylceramides with glycosyl iodides. This direct glycosylation reaction reduces the overall number of synthetic steps and provides rapid access to ,-glycosphingolipids such as GalCer, ,-lactosylceramide, and iGB3 in good yield and with complete chemo- and stereoselectivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Synthesis and Hormonal Activity of the (25S)-Cholesten-26-oic Acids , Potent Ligands for the DAF-12 Receptor in Caenorhabditis elegansEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2009René Martin Abstract Using a highly stereoselective Evans aldol reaction for the introduction of the stereogenic center at C-25, we describe an efficient synthesis of the orthogonally diprotected (25S)-26-hydroxycholesterol 11. In a few synthetic steps, this crucial intermediate 11 has been converted into the four (25S)-cholesten-26-oic acids 1,4, which have been obtained in 12,15 steps and 19,53,% overall yield based on commercially available 3,-hydroxychol-5-en-24-oic acid (5). Our biological studies of the compounds 1,4 reveal that (25S)-,7 -dafachronic acid (1) represents the most active steroidal ligand for the hormonal receptor DAF-12 in Caenorhabditis elegans. Moreover, the saturated (25S)-dafachronic acid (3) represents a new ligand for this receptor and the (25S)-steroidal acids are more active as compared to their corresponding (25R)-counterparts.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Stereocontrolled Preparation of Fully Substituted Cyclopentanes: Relevance to Total SynthesisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 10 2009Brian Heasley Abstract This Microreview aims to identify important advances in the asymmetric synthesis of fully substituted five-membered carbocyclic ring systems. Recent efforts directed towards the intricate and densely functionalized core substructures of three distinct classes of cyclopentane-based natural products will be examined. Strategies featuring high levels of stereocontrol and/or conciseness in the total number of synthetic steps required to access complex natural product ring fragments are highlighted. Stereoselective Diels,Alder cycloaddition approaches to access functionalized norbornene intermediates as latent chiral cyclopentanes in the tradition of Corey's elegant prostaglandin studies are a recurring theme. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] One-Pot Synthesis of Quinoline Derivatives Directly from Terminal Alkynes via Sequential Ruthenium(II) and Acid CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Min Zhang Abstract A convenient one-pot synthesis of 2,3-disubstituted, 2,3,6-trisubstituted, and 2,3,6,7-tetrasubstituted quinoline analogues from terminal alkynes via sequential ruthenium(II) and para -toluenesulfonic acid (p -TSA) co-catalyzed reactions is described. The catalytic process is shown to take place first via intermediate formation of an allyl ketone and then addition of an aniline derivative to the allyl ketone. The p -TSA is a catalyst for both allyl ketone and quinoline synthetic steps. The method allowed us to synthesize a wide range of quinoline derivatives and introduce different substituents by employing various simple starting materials. The reaction allows the synthesis of halogen-containing products. [source] Arborescent polymers and other dendrigraft polymers: A journey into structural diversityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007Mario Gauthier Abstract Arborescent polymers are characterized by a dendritic, multilevel branched architecture derived from successive grafting reactions. In spite of their much larger size, these materials display properties analogous to dendrimers and hyperbranched polymers, the two other dendritic polymer families. The distinguishing features of arborescent polymers are their assembly from polymeric building blocks of uniform size and their very high molecular weights attained in few synthetic steps. This article offers an overview of the historical aspects of the development of dendrigraft polymers, starting from our initial efforts on the synthesis of arborescent polystyrenes. Major subsequent developments in the synthetic techniques from our and other research groups allowing the synthesis of dendrigraft copolymers, tailoring of the structural characteristics of the molecules, and further simplifications to their synthesis are also reviewed, with emphasis over the broad range of architectures attainable in these systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3803,3810, 2007 [source] A Combined ESI- and MALDI-MS(/MS) Study of Peripherally Persulfonylated Dendrimers: False Negative Results by MALDI-MS and Analysis of Defects,CHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2005Thorsten Felder Dipl.-Chem. Abstract Mass spectrometry, in particular MALDI-MS, has often been used as a valuable means to characterize dendritic molecules with respect to their molecular masses. Also, it is a valuable tool for analyzing potential defects in their structure which result from incomplete synthetic steps. This article presents a comparison of ESI and MALDI mass spectrometric experiments on dendrimers persulfonylated at their periphery. While the ESI mass spectra easily permit impurities and defects to be identified and thus provide evidence for sample purity, reactions with acidic matrices occur during the MALDI process. The resulting defects are identical to those expected from incomplete substitution. Thus, in these cases, MALDI-MS yields false negative results. With mass-selected, ESI-generated ions, collision experiments were performed in an FT-ICR mass spectrometer cell to provide detailed insight into the fragmentation patterns of the various dendrimers. Different fragmentation patterns are observed depending on the exact structure of the dendrimer. Also, the nature of the charge is important. The fragmentation reactions for protonated species differ much from those binding a sodium or potassium ion. These differences can be traced back to different sites for binding H+ versus Na+ or K+. Tandem MS experiments on mass-selected dendrimer ions with defects can be used to distinguish different types of defects. A concise structural assignment can thus be made on the basis of these experiments. Even mixtures of two isobaric defect variants with the same elemental composition can be identified. Massenspektrometrie, insbesondere MALDI-MS wurde oft als wertvolle Analysenmethode für die Charakterisierung von Dendrimeren hinsichtlich ihrer Molekülmasse, aber auch hinsichtlich einer Analyse potentieller Strukturdefekte eingesetzt, die aus unvollständig verlaufenden Synthesestufen resultieren. In diesem Artikel berichten wir über einen Vergleich von ESI- und MALDI-massenspektrometrischen Experimenten mit an ihrer Peripherie persulfonylierten Dendrimeren. Während die ESI-Massenspektren eine einfache Identifizierung von Verunreinigungen und Defekten erlauben und damit eine Reinheitskontrolle ermöglichen, laufen während der Ionisierung mittels MALDI Reaktionen mit sauren Matrices ab, die genau solche Defekte erzeugen, wie man sie aus einer unvollständigen Synthese erwarten würde. MALDI-MS führt hier also zu einem falsch-negativen Ergebnis. Mit massenselektierten Ionen aus der Electrospray-Ionisierung wurden Stoßexperimente in einer FT-ICR-Zelle durchgeführt, um einen detaillierten Einblick in das Fragmentierungsmuster der verschiedenen Dendrimere zu erhalten. Man beobachtet unterschiedliche Fragmentierungsmuster in Abhängigkeit von der genauen Struktur der Dendrimere. Auch die Art der Ladung ist wichtig, da die Fragmentierungswege der protonierten Dendrimere sich deutlich von denen ihrer Na+ - und K+ -Addukte unterscheiden. Diese Unterschiede können auf unterschiedliche Bindungsstellen für H+gegenüber Na+oder K+zurückgeführt werden. Tandem MS-Experimente mit massenselektierten, strukturdefekten Dendrimer-Ionen erlauben eine genaue Unterscheidung verschiedener Typen von Defekten. Sie können daher für eine detaillierte Strukturaufklärung verwendet werden. Sogar Mischungen zweier isobarer Defektvarianten mit gleicher Elementarzusammensetzung werden zuverlässig identifiziert. [source] | ||||||||||