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Showing 1 to 20 of 161 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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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 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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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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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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Design and synthesis of suitable phototriggers for a chiroptical liquid crystal switch
… chiral arylmethylene cyclohexanes in both racemic and optically active forms for use as potential photoresolvable mesogens. It was found that these compounds have two spectrally overlapping chromophores which lead to enhanced circular dichroism. With appropriate substituents, some of them …
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