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Showing 1 to 20 of 93 for “"protecting group"”.
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Synthesis of sila-analogs and silicon-containing derivatives of drugs and development and application of the Si-2,4,6-trimethoxyphenyl moiety as a novel protecting group in organosilicon chemistry
… moiety is described as a novel, acid-labile protecting group in organosilicon chemistry. The synthesis of chlorotris(chloromethyl)silane and tris(chloromethyl)methoxysilane is described.
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Generating structural diversity in \(\alpha\)[alpha],\(\alpha\)[alpha]-difluoromethyl ketones
… Due to the difficulties with cleavage of this protecting group, the synthesis and potential application of an \(N\)-ethyl-\(N\)-(2-methylallyl)carbamate has been studied. A 2-methoxyethoxymethyl (MEM) protecting group strategy proved very successful for the synthesis of a range of …
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Struktur, Hydroxyalkylierung und Aminoalkylierung von Titanaallylsulfoximinen: Enantioselektive Synthese ungesättigter Alpha-Aminosäuren
… alpha-amino acid derivatives. The N-sulfonyl-protecting-group could be cleaved under mild conditions. The N-methylsulfonimidoyl-protecting-group was substituted using a diphenylzinc / Ni(dppp)Cl2 mediated cross-coupling-reaction. Thus a concept for the synthesis of beta,delta-substituted …
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Total Synthesis and Stereochemical Revision of Pestalospirane B
… effort focused on identifying a suitable protecting group for the phenol group during the synthsis of the natural product. Initial attempts at late stage deprotection of isopropyl dimer 314 were unsucessful, thus a revision in protecting group strategy was enforced where access to the …
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Progress Toward the Synthesis of 3-Methoxyflavones as Potential Antioxidants, Neuroprotective Agents, and Trifluoromethylated 19F NMR Probes
… due to the presence of more than one hydroxyl group. Direct cyclization was not successful in any of the attempts. However, by using a silyl protecting group, the cyclization was feasible. Other reactions like the Friedel-Crafts acylation and selective protection of phenols were also difficult.
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Development of a continuous-flow synthesis of neostigmine methylsulfate and studies toward a continuous-flow synthesis of lisinopril
… isolation of several synthetic intermediates and protecting group manipulations, thus, development of an efficient continuous synthesis would provide great benefit. Herein we describe our investigation of several routes to generate intermediates of lisinopril with the end goal of a fully …
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Development of nitrogen protecting groups and synthesis and complexation of bridged bis-tetraazamacrocycles
<p>The development of nitrogen-protecting groups that are orthogonal to the N-benzyl group for use in cross-bridged tetraazamacrocycles and the synthesis and complexation of bridged bis-tetraazamacrocycles are presented. The allyl, p-methoxybenzyl (PMB), and 2-naphthylmethyl (Nap) …
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Synthesis of Delta(3)-Imidazolines as Latent Forms of Peptidyl Trifluoromethyl Ketones
… The imidazolines then functioned as a protecting group for the trifluoromethyl ketones during typical peptide Fmoc deprotection and elongation reactions. In the final step, the imidazoline was hydrolyzed with dilute acid, which afforded the trifluoromethyl ketone in good yield. This …
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An Approach to the Total Synthesis of the Protein Phosphatase 1 and 2A Inhibitor Microcystin -Lr
… routes to the natural product utilizing several protecting group strategies. Extensive studies were required to gain insight into the susceptibility of the intermediates to reaction conditions. This work has led to the first synthetic route to the intermediate microcystin-LR-di-Boc-guanidine …
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Synthesis of Deoxysugars through Manganese-promoted Redox Isomerization
… synthetic routes towards deoxysugars rely on protecting groups to achieve selective outcomes. Here we report a concise synthetic strategy to access a diverse set of 2- and 4-deoxysugars using a Mn-promoted redox isomerization step that avoids lengthy protecting group manipulations. We …
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Development of Transition Metal-Catalyzed Borylation Protocols using Symmetrical and Unsymmetrical Diboron Reagents
… diboron reagent, pinB-Bdan. This alternative protecting group has emerged as an orthogonal protecting group and alters the reactivity of the boron moiety. Activation of the pinacol moiety to form the Lewis acid-base adduct allowed for the chemoselective transfer of the 1,8- diaminonapthalene …
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Syntheses of Azido- and Diazido- 10-Methylacridinium Salts.
… synthetic scheme involved reduction of the nitro group to an amino function, acetylation of the primary amino group, methylation of the ring nitrogen with subsequent removal of the protecting group and diazotization of the primary amine followed by nucleophilic displacement of the diazonium salt …
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Stereoselective synthesis of piperidines
… vi which, after cleavage of the chiral protecting group gave the desired enantiomerically-enriched, 2-substituted piperidines vii. [Illustrated] The piperidines vii were produced in good overall yield, high purity, and good to excellent stereochemical purity. By switching the enantiomer …
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Synthesis and biological evaluation of potential DNA cross-linking agents based on pyrrolizidine alkaloids
… of a potential water soluble photolabile protecting group is also described. In addition, the biological evaluation of the synthesized pyrrolizidine progenitors was investigated.
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Synthesis And Á-Stereoselective Sialylation Of Kdn And Late Stage Modification Of Neuraminic Acid Sialosides
… for the KDN series by means of a 4,5-O-carbonate group installed on the pyranose ring. The 4,5-O-carbonate moiety proved to be an excellent á-directing group in sialylation for a wide array of acceptors independent of the anomeric configuration of the donor, and provided high yields by inhibiting …
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Studies in Asymmetric Catalysis: Lewis Base Catalyzed, Enantioselective Addition of Trimethylsilyl Cyanide, Trimethylsilyltrifluoromethane, and Glycolate-Derived Silyl Ketene Acetals to Aldehydes
… derived from methyl glycolates with a large protecting group on alpha-oxygen provide enantiomerically enriched alpha,beta-dihydroxy esters with high syn-diastereoselectivity, whereas the tert-butyldimethylsilyl ketene acetals derived from bulky esters of alpha-methoxy acetic acid provide …
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Design, Synthesis and Biological Properties of Fluorinated Estrogens, Progestins and Androgens, Potential Imaging Agents for Receptor-Positive Mammary and Prostate Tumors (fluorine-18)
… sulfate was developed by modifying the C-3 protecting group of the sulfate precursor and reaction time, temperature and solvent.
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Organic reactions catalyzed by copper(I) hydride complexes
… allylation reactions. By modulating the nitrogen-protecting group, either highly branched- or linear-selective addition can be achieved from the same allene. Both reactions exhibit excellent diastereoselectivity and broad functional-group tolerance. Good enantioselectivity can also be achieved in …
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Development of an Improved Synthesis of S-D-Ribosyl-L-Homocysteine (SRH) and Progress Toward SRH Analogs Modified at the C3 Position
… of SRH through the exploration of different protecting group strategies. The knowledge gained from the improved synthesis of SRH is then applied toward the synthesis of SRH analogues with increased steric bulk installed through use of a stereoselective anti-Mannich reaction. SRH analogues …
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Synthesis Of Oligosaccharide Mimetics By The Desulfurative Rearrangement Of Allylic Disulfides And Stereoelectronic Influence Of C-O Bonds On C- And O-Glycosylation
… the β-(1→6)-N-acetyl glucosamine polymer. Small, protecting group-free, pre-assembled sugar units are linked together into larger oligosaccharide chains by the desulfurative rearrangement of allylic disulfides.</p> <p>The first part of chapter three presents the general mechanistic aspects of …
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