dc.contributor.author
Greis, Kim
dc.date.accessioned
2023-07-21T08:18:31Z
dc.date.available
2023-07-21T08:18:31Z
dc.identifier.uri
https://refubium.fu-berlin.de/handle/fub188/40105
dc.identifier.uri
http://dx.doi.org/10.17169/refubium-39827
dc.description.abstract
Knowing the structure of reactive intermediates can yield unprecedented insight into organic reaction mechanisms. In particular for glycosyl cations – the reactive intermediates in glycosylations – the stereoselectivity of the reaction could be predicted by knowing the structure of the intermediate. The structure reveals whether an acyl protecting group of the monosaccharide unit interacts with the positively charged anomeric carbon so that it would shield one side from nucleophilic attack and thus steer the stereoselectivity of the reaction. These postulated approaches have been termed neighboring-group and remote participation. However, the short lifetime of reactive intermediates impedes their structural characterization in solution. Hence, for glycosyl cations, the structure remained elusive until very recently. These intermediates are not intrinsically unstable, but well-defined minima on the potential energy surface. Therefore, the ionic intermediates can be generated inside the vacuum of a mass spectrometer, free from nucleophiles or solvent molecules. In this environment, the isolated intermediates are stable and can subsequently be characterized using spectrometric or spectroscopic techniques. Recent advances in instrumentation allow coupling mass spectrometers with infrared lasers for infrared ion spectroscopy. Thus, highly-resolved infrared spectra of the analyte ions can be obtained by using cryogenic infrared spectroscopy in helium nanodroplets. To assign the obtained spectrum to a structure, it can be compared to harmonic frequencies of promising candidate structures calculated using density functional theory. This workflow was successfully used to determine the structure of several glycosyl cations, based on which, a new selective building block for 1,2-cis galactosylations was developed and its stereoselectivity was rationalized. Furthermore, it was determined that c-fragments of RNA dinucleotides are identical to the intermediate of RNA autohydrolysis. Finally, potentially antiaromatic carbocations were investigated.
en
dc.format.extent
XIV, 444 Seiten
dc.rights.uri
https://creativecommons.org/licenses/by-nc/4.0/
dc.subject
Mass Spectrometry
en
dc.subject
Infrared Spectroscopy
en
dc.subject
Carbohydrates
en
dc.subject
Density Functional Theory
en
dc.subject.ddc
500 Naturwissenschaften und Mathematik::540 Chemie::547 Organische Chemie
dc.subject.ddc
500 Naturwissenschaften und Mathematik::540 Chemie::541 Physikalische Chemie
dc.subject.ddc
500 Naturwissenschaften und Mathematik::540 Chemie::543 Analytische Chemie
dc.title
Structural Analysis of Glycosyl Cations and Other Intermediates Using Cryogenic Infrared Spectroscopy
dc.contributor.gender
male
dc.contributor.inspector
Müller, Christian
dc.contributor.inspector
Papp, Christian
dc.contributor.inspector
Götze, Michael
dc.contributor.firstReferee
Pagel, Kevin
dc.contributor.furtherReferee
von Helden, Gert
dc.date.accepted
2023-07-12
dc.identifier.urn
urn:nbn:de:kobv:188-refubium-40105-8
dc.title.translated
Strukturanalyse von Glykosylkationen und anderen Intermediaten mittels kryogener Infrarotspektroskopie
ger
refubium.affiliation
Biologie, Chemie, Pharmazie
dcterms.accessRights.dnb
free
dcterms.accessRights.openaire
open access
dcterms.accessRights.proquest
accept