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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"ketal"”.
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A study of activated ketal reduction with borane dimenthyl sulphide
… recent times, is the dissociative reduction of ketals to afford ethers as protected secondary derivatives and a number of approaches accomplishing a high degree of stereoselectivity have been developed. This thesis describes a study of a novel reagent combination, namely borane dimethyl sulphide …
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Synthesis Of 6-Nor-5,7-Seco-5-Ketal- 7,7-Diphenylcholest-7-Ene
Steroids in which one or more of the carbocyclic rings is replaced by heterocyclic systems may be expected to have interesting physiological properties. Compounds of this kind with vicinal diaza systems are rare, and none in the B-ring of cholesterol is known. | The present investigation was …
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A facile conversion of beta-keto carbonyl compounds to alpha, beta-unsaturated-gamma-oxo carbonyl systems and a study of ketal -derived oxonium ylides
… synthesis of patulolide B. An extensive study of ketal-derived oxonium ylides and the subsequent rearrangement was also accomplished. The application of this chemistry was applied to Bu-2313 and a unique class of compounds known as the hyperolactones.</p>
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Efforts towards the Total Synthesis of Azaspiracid-3
… segment and C13-C22 segment. The trioxadispiroketal skeleton was constructed under the influence of acid catalysis. The EFGHI domain highlighted a chelate controlled Mukaiyama aldol reaction to produce C22-C40 linear precursor, and a DIHMA process to assemble the bridged ketal. With the …
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Radical cyclisation studies of chiral α-acylamino radicals : a model study towards Tacaman indole alkaloid synthesis
… Those radicals incorporating an isopropylidene ketal at the 4 and 5 positions as chiral auxiliary showed excellent regio- and stereoselectivity. Out of a possible 4 diastereomers, only two were obtained in a 2:8 ratio. It was established that the isopropylidene ketal directed the cyclisation …
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Synthesis and characterization of pH/temperature dual sensitive multiblock copolymer for drug delivery
… by polycondensation between an acid-labile ketal linker, 2,2-bis(aminoethoxy)propane (BAP) and Pluronic® P104 using L-lysine diisocyanate ethyl ester (LDI) or 1,6-Diisocyanatohexane (HDI). The gelation temperature of 20% (w/v) MBCP was in the range of 29 to 31 ºC when tested with three …
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Chemistry with chiral lithium amides: enantiotopic group and face-selective reactions
… products: 1,4- cyclohexanedione monoethylene ketal and tropinone.The aldol reaction between the lithium enolate of 1,4-cyclohexanedione monoethylene ketal and benzaldehyde demonstrated the high diastereoselectivity (up to 98% de) and the moderate to high enantioselectivity (up to 75% ee) …
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Studies toward a total synthesis of (±)-subergorgic acid
… of (±)-subergorgic acid (8), the known keto ketal 101 was converted into the enone 100. Copper(I)-catalyzed conjugate addition of the Grignard reagent 91 to the enone 100, followed by intramolecular alkylation of the intermediate enolate anion, provided the triquinane 99. Sequential …
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Synthesis of derivatives of 4H-cyclopenta[ def]phenanthren-4-one and development of synthetic strategies for the polycyclic aromatic hydrocarbons with carbon frameworks represented on the surface of C60
… with tri-n-butyltin hydride then gave the ketal 62 in 46% overall yield from 56a. Hydrolysis of the ketal 62 gave the ketone 51 in 97% yield.;Another derivative of 4H-cyclopenta[def]phenanthren-4-one, 87, was also synthesized from 54 and 2 equivalents of …
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Synthesis and characterization of molecules for electron transfer research.
… was reacted with cyclohexanedione, mono ethylene ketal. The resulting alcohol was changed to the donor precursor through the following functional group transformation steps: dehydration, hydrogenation, deketalization and bromination. 1,4-Dibenzyloxybromobenzene, the precursor for the acceptor, was …
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The Total Synthesis of (-)-Prezizaene, (-)-Prezizanol, and Other Perzizanoid Sesquiterpenes
… ethylene ketal as a single isomer after crystallization. An X-ray structure determination confirmed the all cis stereochemistry at the three chiral centers. Reduction and hydrolysis afforded a dimethyl ketone which was identical with a sample prepared …
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The design, synthesis and properties of pressure-processable biodegradable block copolymers
… the poly([epsilon]-caprolactone-ran-5 ethylene ketal [epsilon]-caprolactone)-block-poly(lactic acid) (PmCL-b-PLA) system exhibit pressure- induced miscibility, and small angle x-ray scattering (SAXS) revealed that the position of the upper disorder-to-order temperature (UDOT) in those systems is …
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Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.
A series of homochiral ene ketals were prepared and subjected to the Simmons-Smith cyclopropanation. A mechanistic model was formulated to explain the observed diastereoselectivity seen for the common ring systems. Diastereoselectivity is thought to result from preferential chelation of the …
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I Progress towards the synthesis of plakortether B through a zinc-mediated homologation II Synthesis of novel hydroxy-cyclopropyl peptides isosteres
… amide could be converted into a furanyl-ketal with high stereocontrol at two chiral centers. The homologation-aldol reaction was followed by a cyclization-allylation to obtain the plakortether backbone.</p><p>During the synthesis of plakortether B, a serendipitous byproduct was identified …
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Trifluoroethyl enol ethers, dienol ethers, and acetals: an investigation of their preparations, reactivities, and synthetic applications
… studied were trifluoroethoxy substituted ketals, enol ethers, and dienol ethers. The ketal and enol ether work involved developing methodology for the large scale preparation of these structures as well as studies detailing their behavior. For the TFE ketals, preparation involved an …
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Cumarin- und DBD-Farbstoffe als Fluoreszenzsonden
… um Cou- und DBD-funktionalisierte Oligo-Spiro-Ketal-Stäbe (OSTK) und ihre Eigenschaften als Membransonden zu untersuchen. Der letzte Teil beschäftigt sich mit der Synthese und der Charakterisierung von Cou- und DBD-funktionalisierten Polyprolinen als Referenzsysteme für …
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Dynamics and Catalytic Resolution of Selected Chiral Organolithiums
… N-Boc-2-lithiopiperidine, and the ethylene ketal of N-Boc-2-lithio-4-oxopiperidine were selected. The barriers to racemization and dynamic thermodynamic resolution (DTR) of these compounds were measured in the presence of various diamine ligands. Using the thermodynamic parameters to guide …
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Asymmetric Synthesis of 1,3-Amino Alcohols and Tropinone Derivatives From Enantiopure Sulfinimines
… intramolecular cyclization of acyclic ketal-protected N-sulfinyl ketones. After reaction with an acylating agent, the tropinone nucleus can be formed through an intramolecular Mannich reaction of an N-acyl iminium ion.
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Funktionalisierte OS(T)K-Stäbe und Sensorfluorophore zur optischen Sensorik
… Arbeit wurden zum einen erste Oligospiro(thio)ketal (OS(T)K)-basierte Modellsysteme (molekulare Sonden) für abstandsabhängige Messungen mittels Förster-Resonanz-Energietransfer (FRET) und zum anderen Sensorfluorophore, basierend auf einem DBD-Fluorophor und BAPTA, zur Messung der …
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Structural studies of the capsular polysaccharides from some strains of Klebsiella and Cryptococcus neoformans micro-organisms
… three to five hexose residues, with pyruvic acid ketal and 0-acetyl groups also present in some of the polysaccharides. Graded acid hydrolysis, monitored by gel-permeation chromato graphy, has been used to study the degradation of each polysaccharide to the structurally significant …
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