Competing C-4 and C-5-Acyl Stabilization of Uronic Acid Glycosyl Cations.
Chemistry
; 28(63): e202201724, 2022 Nov 11.
Article
em En
| MEDLINE
| ID: mdl-35959853
ABSTRACT
Uronic acids are carbohydrates carrying a terminal carboxylic acid and have a unique reactivity in stereoselective glycosylation reactions. Herein, the competing intramolecular stabilization of uronic acid cations by the C-5 carboxylic acid or the C-4 acetyl group was studied with infrared ion spectroscopy (IRIS). IRIS reveals that a mixture of bridged ions is formed, in which the mixture is driven towards the C-1,C-5 dioxolanium ion when the C-5,C-2-relationship is cis, and towards the formation of the C-1,C-4 dioxepanium ion when this relation is trans. Isomer-population analysis and interconversion barrier computations show that the two bridged structures are not in dynamic equilibrium and that their ratio parallels the density functional theory computed stability of the structures. These studies reveal how the intrinsic interplay of the different functional groups influences the formation of the different regioisomeric products.
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Base de dados:
MEDLINE
Assunto principal:
Ácidos Urônicos
/
Ácidos Carboxílicos
Idioma:
En
Ano de publicação:
2022
Tipo de documento:
Article