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Showing 1 to 20 of 183 for “"Racemic"”.
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Deracemizing Racemic Compounds
Contains fulltext : 143566.pdf (Publisher’s version ) (Open Access)
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Methodology studies on the synthesis of chiral, non-racemic aza-quaternary centres
The synthesis of chiral, non-racemic aza-quaternary centres is one of the biggest challenges in current organic synthesis. Many natural products contain them and as a privileged biological motif they are of interest to medicinal chemistry. The structural complexities of these functionalities …
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Organocatalytic synthesis of chiral non-racemic aziridines, labelled with 2H, 15N, 13C stable isotopes
Aziridines are ‘keystone’ synthetic building blocks - relatively reactive, three-membered heterocycles with the potential for generating ‘secondary’ high value entities such as α- or β-amino acids via ring-opening reactions. Within this thesis, a one-pot asymmetric organocatalytic methodology is …
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The preparation of racemic and optically active beta-amino-acids and their utilisation in peptide formation.
… preparation of linear and cyclic peptides of racemic and optically active B-aminobutyric acid. B-Amino acid cyclisation studies by Barker 84 had led to the conclusion that oxazinones could only be obtained from saturated B-benzamido—acids containing quaternary B-cabon atoms, while other …
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Studies towards the Organocatalytic ‘Dialled In’ Synthesis of Chiral, Non-Racemic Aziridines, and Amino Acids, Containing Multiple Isotopic Labels
Within this thesis, a highly effective one-pot methodology (based around the use of the organocatalyst pyridinium triflate) has been developed for the highly cis-selective synthesis of N-aryl 3-aryl-aziridine-2-carboxylates as racemates in yields of up to 80 %. This methodology has been extended by …
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New methodology for the synthesis of chiral, non-racemic a-tertiary amine centres: application to the synthesis of the marine alkaloid lepadiformine
… methodology for the synthesis of a chiral, non-racemic quaternary carbon bearing an α-nitrogen (an α-tertiary amine or ATA) continues to be an active area of modern research in current synthetic organic chemistry. As a privileged biological scaffold, ATAs are widespread amongst bioactive natural …
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Palladium-katalysierte kinetische Racematspaltung allylischer Carbonate mit S-Nukleophilen und enantioselektive Umlagerung allylischer O-Sulfinate : asymmetrische Synthese von allylischern Sulfiden und Sulfonen
… reactions of symmetrically disubstituted racemic allylic carbonates, being either cyclic or acyclic, with 2-pyrimidinethiol in the presence of N,N'-(1R,2R)-1,2-cyclohexanediyl-bis[2-(diphenylphosphino)-benzamide] BPA as ligand proceed with excellent levels of enantio-selectivity in both …
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New routes to enantioenriched substances through small organic molecules
… (n salt, p salt and p1,n1 salt) between non-racemic trans-chrysanthemic acid (trans-ChA) and pure enantiomers of threo-2-dimethylamino-1-phenyl-1,3-propanediol (DMPP). The occurrence of p1,n1 salt formation can have profound effects on enantiomer separation of scalemic (non-racemic) mixtures. …
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A new cyclohexyl-based chiral auxiliary: application in the total synthesis of (+)-linalool oxide
Seven different racemic cyclohexyl-based chiral auxiliaries (2.4-2.10) were synthesised in moderate to good yields (38-85%) by nucleophilic opening of cyclohexene oxide using carbanions. The racemic cyclohexyl-based chiral auxiliaries were coupled with the 6-methyl-2- methylenehept-5-enoyl chloride …
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RECENT ADVANCES IN IMINIUM SALT CATALYSED ASYMMETRIC EPOXIDATION
… this reaction towards the kinetic resolution of racemic olefins. Chapter two is separated into two key areas; (i) asymmetric epoxidation as a tool in the kinetic resolution of racemic chromene substrates, and (ii) investigations into the asymmetric epoxidation of new N-protected dihydroquinoline …
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Mechanistic Studies on Memory of Chirality Alkylations of 1,4-Benzodiazepin-2-ones & Structure-based Design of Insecticidal AChE Inhibitors for Malaria Mosquito, Anopheles gambiae
… relies upon the intermediacy of transiently non-racemic reactive species. In these reactions the configuration of the sole stereogenic center of the enantiopure starting material is "memorized" by a chiral non-racemic conformation in the intermediate; trapping then captures the stereochemical …
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A novel, versatile D-BCD steroid construction strategy, illustrated by the total syntheses of estrone and desogestrel
… C8, C13 and C14 in a single-pot operation. The racemic total synthesis of desogestrel includes a successful domino anionic cyclisation leading to the formation of the steroid C and B rings in a single operation with complete stereocontrol at C9. The ?-keto phosphonates obtained were subsequently …
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Thiopyran route to polypropionates : simultaneous-two directional and enantiotopic group selective aldol reactions
… An extension of this strategy to generate non-racemic tetra- and hexapropionate fragments involved the use of non-racemic 119 which was obtained via resolution of the acid derivate 131. Part of the present work concerns the preparation of non-racemic 119 via enantioselective protonation of …
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The Stereochemistry of Organosilicon and Complex Inorganic Compounds: i.a Study of the Mechanism of a Nucleophilic Substitution Reaction on an Organosilicon Compound. Ii. The Partial Resolution of Racemic Propylenediamine Through an Optically Active Complex Inorganic Compound
Made available in DSpace on 2014-12-05T19:35:58Z (GMT). No. of bitstreams: 1 0009096.pdf: 3450031 bytes, checksum: dbde489183679109dfa2241d3b8a5694 (MD5) Previous issue date: 1954
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The chemistry of thujone : new enantioselective syntheses of Ambrox[Registered trade mark] and Epi-Ambrox
… enone 143. As a model study for the synthesis of racemic 2 and 3, a synthetic sequence starting with a cyclohexanone derivative has also been developed to afford the racemic intermediate143. Acid catalyzed Robinson annelation of 2-methylcyclohexanone with1-chloropentan-3-one gave enone 165. …
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Synthesis of aza-tryptophan derivatives.
The preparation of racemic 7-azatryptophan from 7-azaindole has been accomplished. The aldol condensation of 1-tert-butoxycarbonyl-3-formyl-7-azaindole with methyl hippurate installed the carbon framework necessary for the intended product. Subsequent deoxygenation and deprotection of the indole, …
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Nickel-catalyzed cross-couplings of unactivated secondary and tertiary alkyl halides and photoinduced copper-mediated asymmetric C-N cross-couplings
… via the stereoconvergent cross-coupling of racemic secondary [gamma]-chloroamides with primary alkylboranes. Section 1.2 describes the first Suzuki carbon-carbon bond-forming reaction using tertiary alkyl halides as electrophiles; specifically, unactivated tertiary alkyl bromides are …
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Flexible access to an array of optically-enriched conformationally-locked bicyclic morpholines and approaching bridged bicyclic piperazines
… scaffold, with, in the first instance, a racemic route being targeted. The initial proposed bridged morpholine precursor, an α,β-unsaturated ester, was synthesised, however, the key final step to deliver the desired bridged morpholine proved to be unsuccessful. Following on from this, an …
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Novel methods and processes for the chiral resolution of fine chemicals
… on the solubility and phase diagrams ofthree racemic compound-forming systems are described. This preliminary study of effectspermits the development of a method to accurately estimate the eutectic points and phasediagrams of these systems. Additionally, the method also gives the possibility …
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Werner clathrates with potential chiral selectivity : preliminary investigations
… enantiomerically pure amine ligand and from the racemic mixture, as well as its clathrate with sec-butylbenzene have been determined by x-ray diffraction.
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