Investigations of the Carbonyl-Olefin Metathesis and β-Glycosylation inside the Supramolecular Resorcinarene Capsule

Huck, Fabian. Investigations of the Carbonyl-Olefin Metathesis and β-Glycosylation inside the Supramolecular Resorcinarene Capsule. 2022, Doctoral Thesis, University of Basel, Faculty of Science.

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Official URL: https://edoc.unibas.ch/89777/

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In order to access environmentally friendly chemistry, new «green» catalysts have to be developed and applied in novel and efficient reactions. The resorcinarene hexamer II can be regarded as such and has already demonstrated its capability to access complex reaction cascades like tail-to-head terpene cyclization.
In the first part of this work, the capability of II to catalyze the emerging carbonyl-olefin metathesis in presence of HCl was investigated. Carbonyl-olefin metathesis is a comparably new reaction for carbon-carbon bond formations.
First, the synthesis of 2-5-dihydropyrroles was investigated. The starting material was synthesized from chiral amino acids with a tosyl protecting group. Although good yields were obtained for the glycine and alanine derived substrates, larger α-substituents lead to little product formation on the one hand and more dealkylation on the other. Mesyl and 4-trifluoromethylbenzenesulfonyl protecting groups were tested as an alternative. Protection with mesyl showed good yields but astonishingly the best result was obtained with the phenylalanine substrate, the biggest amino acid derivative tested in this substrate scope. 4-trifluoromethylbenzenesulfonyl derivative on the other hand resulted in low yields and mainly decomposition of starting material.
Mechanistic investigations of three representative substrates by an Eyring analysis and determination of secondary isotopic effects showed that diverging rate-limiting steps are possible for different substrates. The experiments were repeated with the literature known catalyst iron(III)chloride with a similar observation. Attempts to intercept the intermediate carbocations with mechanistic probes were successful. Nevertheless, subsequent studies showed that the ortho-phenol group in the mechanistic probe alters the reaction pathway and therefore cannot be used to make statements about the general mechanism.
In order to expand the substrate and reaction scope, alkyl ketones and the intermolecular ring-opening cross carbonyl-olefin metathesis were tested. Unfortunately, no promising results were obtained in both cases.
In the second part of this thesis, the mechanism of β-glycosylation inside hexamer II was investigated by determination of the reaction order, determination of the secondary kinetic isotope effect, and by a proton inventory study. The experimentally determined reaction order and the secondary kinetic isotope effect were indicative of a loose SN2 transition state. Subsequent calculations suggested a dual activation of the glycosyl donor and the nucleophile via a communicating hydrogen bond network. Results from the proton inventory study indeed suggest the participation of more than two hydrogen bonds in the transition state.
Advisors:Tiefenbacher, Konrad Karl and Housecraft, Catherine and Nguyen Viet, Hung
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Synthesis of Functional Modules (Tiefenbacher)
Item Type:Thesis
Thesis Subtype:Doctoral Thesis
Thesis no:14780
Thesis status:Complete
Number of Pages:VIII, 243
Identification Number:
  • urn: urn:nbn:ch:bel-bau-diss147809
edoc DOI:
Last Modified:01 Sep 2022 13:54
Deposited On:01 Sep 2022 13:54

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