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University of Iowa

1. Banerjee, Koushik. Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins.

Degree: PhD, Chemistry, 2011, University of Iowa

Mn-Mediated radical addition has been developed within the Friestad laboratory as a versatile method toward addition to C=N bonds. N-Acylhydrazones generated by condensation between an aldehyde and an N-acylamine serves as the substrate toward radical addition. A bulky directed group attached with the N-acyl moiety and restricted rotation around N-N bond due to a three point chelation with a Lewis acid differentiates the faces of the C=N bond of the N-acylhydrazones. Radical generation initiated by photolysis of Mn2(CO)10 causing homolysis of C-X bond in alkyl halide serves as the radical donor to the N-acylhydrazones. Radical addition thereafter occurs stereoselectively from the less hindered face of the C=N bond of the N-acylhydrazones. The product N-acylhydrazines can be effectively transformed to α-chiral amines. In this thesis, a new protocol toward generation of non-proteogenic γ-amino esters using Mn-mediated radical addition has been described. Moreover, the utility of the Mn-mediated radical addition has been demonstrated through studies toward synthesis of tubulysin U and V. Chapter 3 describes a new strategy for asymmetric synthesis of γ-amino esters starting from non-amino precursors. The α-substituted γ-amino esters are prevalent in drugs, drug candidates, and in peptidomimetics. As a part of progressing the Mn-mediated radical addition reaction, highly stereoselective reactions were devised for addition to N-acylhydrazonoesters in absence of Lewis acid. Spectroscopic investigations were carried out to decipher the Lewis acid chelation of N-acylhydrazones. Finally, a novel microwave mediated trifluoroacylation of N-acylhydrazinoesters facilitated the cleavage of N-N bond to liberate γ-aminoester. Chapter 4 describes application of Mn-mediated radical addition toward synthesis of tubulysin natural products. Tubulysins are natural products, isolated from myxobacteria, that have exhibited potent cytotoxicity toward cancer cells in the picomolar regime. The Mn-mediated radical addition was used to prepare two chiral amine subunits in highly diastereoselective fashion. The subunits were then assembled after required manipulations into the tetrapeptide structure characteristic of tubulysins. This strategy to synthesize tubulysins is the most stereoselective of all efforts toward the synthesis of this molecule. Synthesis toward tubulysin was achieved in 18 steps as the longest linear sequence with a 31% overall yield to tubulysin V in benzyl protected form. Chapter 5 describes a new strategy toward installation of N-hydroxymethyl unit into a peptide chain. N,O-Acetals are acid-base labile species that is present in some tubulysin natural analogs. This new approach exploits Fleming-Tamao oxidation and hence introduce the hydroxymethyl unit of the N,O-acetal in a masked form. Following peptide construction the masked hydroxy group is released to liberate the N-hydroxymethyl moiety. Acylation of the free hydroxy group furnishes the N,O-acetal moiety in a strategy that is potentially… Advisors/Committee Members: Friestad, Gregory K. (supervisor).

Subjects/Keywords: Amine; gamma amino ester; microwave acylation; n,o-acetal; tubulysin; unnatural amino acid; Chemistry

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Banerjee, K. (2011). Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins. (Doctoral Dissertation). University of Iowa. Retrieved from https://ir.uiowa.edu/etd/1121

Chicago Manual of Style (16th Edition):

Banerjee, Koushik. “Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins.” 2011. Doctoral Dissertation, University of Iowa. Accessed September 21, 2019. https://ir.uiowa.edu/etd/1121.

MLA Handbook (7th Edition):

Banerjee, Koushik. “Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins.” 2011. Web. 21 Sep 2019.

Vancouver:

Banerjee K. Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins. [Internet] [Doctoral dissertation]. University of Iowa; 2011. [cited 2019 Sep 21]. Available from: https://ir.uiowa.edu/etd/1121.

Council of Science Editors:

Banerjee K. Investigations in amine chemistry: Mn-Mediated radical addition approach toward gamma amino esters and synthetic studies of the tubulysins. [Doctoral Dissertation]. University of Iowa; 2011. Available from: https://ir.uiowa.edu/etd/1121


Université Paris-Sud – Paris XI

2. Stevenin, Arnaud. Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates.

Degree: Docteur es, Chimie, 2011, Université Paris-Sud – Paris XI

Les symbioses bactérie-légumineuse (nodulation) et champignon-plante (mycorhization) présentent un intérêt agrobiologique et écologique majeur ; elles permettent aux plantes de croître naturellement sur un sol aride et peu fertile. Il a été démontré très récemment que les signaux impliqués dans la mise en place de la symbiose endomycorhizienne à arbuscule (facteurs "Myc") sont très proches de ceux de la nodulation. Il s'agit de molécules appartenant à la famille des lipo-chitooligosaccharides. Afin de réaliser la synthèse de ces molécules, deux nouvelles méthodologies ont été développées. L'ouverture oxydante d'acétals de 4,6-O-benzylidène de plusieurs glycopyranosides (en série gluco, galacto et manno) par le diméthyldioxirane (DMDO) a été étudiée. Le contrôle de la régiosélectivité a été effectué grâce au groupement protecteur introduit sur la fonction alcool de la position 3. La formation directe de β-glycosides de la N-acétyl-D-glucosamine par catalyse au triflate de fer (III) a été étudiée. La réaction a été menée sous irradiation micro-ondes ou en flux continu (système minifluidique Vapourtec®). Une nouvelle stratégie pour la synthèse du facteur [Myc-IV (C16:0, S)] a ensuite été établie. Nous avons utilisé un réactif peu toxique et non odorant pour introduire le motif thio nécessaire à la formation de deux liaisons glycosidiques. Le disaccharide précurseur de l'unité réductrice a été obtenu grâce à la première méthodologie développée au cours de cette thèse.

Arbuscular mycorrhiza (AM) is a root endosymbiosis between plants and fungi. It has an agrobiological interest and a crucial ecological importance because it allows plants to grow on aride and infertile soil. Recently, the structure of the symbiotic signal "Myc factor" was identified as a mixture of lipochitooligosaccharides (LCOs). In order to propose a new synthesis of LCOs, we developed two green methodologies in glycochemistry. We performed the oxidative cleavage of 4,6-O-benzylidene acetals of various glycopyranosides (gluco, manno and galacto series) with dimethyldioxirane (DMDO) and its regioselective control with a suitable protecting group at position 3. We investigated the formation of β-glycoside of N-acetyl-D-glucosamine using catalytic iron (III) triflate. The reaction can be performed using microwave irradiation or, for scale-up synthesis, flow chemistry using Vapourtec® minifluidic system. We establish a new strategy for the total synthesis of the most abundant Myc factor [Myc-IV (C16:0, S)]. We used odorless and few toxic MbpSH reagent to introduce the activated thio residue involved in two glycosylation reactions. The disaccharide acceptor precursor of the reducing end was obtained after oxidative cleavage of the 4,6-O-benzylidene moiety by DMDO.

Advisors/Committee Members: Beau, Jean-Marie (thesis director), Boyer, François-Didier (thesis director).

Subjects/Keywords: Symbiose mycorhizienne; Glycoconjugés bioactifs; Acétals de 4,6-O-benzylidène; Diméthyldioxirane; Régiosélectivité; N-acétyl-D-glucosamine; Triflate de fer (III); Facteur Myc; Lipo-chitooligosaccharide; Thiol non odorant; Mycorrhizal symbiosis; Bioactive glycoconjugates; 4,6-O-benzylidene acetal; Dimethyldioxirane; Regioselectivity; N-acetyl-D-glucosamine; Iron (III) triflate; Myc factor; Odorless thiol; Lipochitooligosaccharide

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Stevenin, A. (2011). Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates. (Doctoral Dissertation). Université Paris-Sud – Paris XI. Retrieved from http://www.theses.fr/2011PA112147

Chicago Manual of Style (16th Edition):

Stevenin, Arnaud. “Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates.” 2011. Doctoral Dissertation, Université Paris-Sud – Paris XI. Accessed September 21, 2019. http://www.theses.fr/2011PA112147.

MLA Handbook (7th Edition):

Stevenin, Arnaud. “Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates.” 2011. Web. 21 Sep 2019.

Vancouver:

Stevenin A. Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates. [Internet] [Doctoral dissertation]. Université Paris-Sud – Paris XI; 2011. [cited 2019 Sep 21]. Available from: http://www.theses.fr/2011PA112147.

Council of Science Editors:

Stevenin A. Symbiose mycorhizienne : développement de nouvelles méthodes pour la synthèse de glycoconjugues bioactifs : Mycorrhizal symbiosis : development of new methods for synthesis of bioactive glycoconjugates. [Doctoral Dissertation]. Université Paris-Sud – Paris XI; 2011. Available from: http://www.theses.fr/2011PA112147

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