Characterization and structural determination of 3A-amino-3A-deoxy-(2AS, 3AS)-cyclodextrins by NMR spectroscopy

Abstract

The proton and carbon nuclear magnetic resonance (NMR) resonances have been assigned for 3A-amino-3A-deoxy-(2AS,3AS)-a-, b-and c-cyclodextrins (CyDs) (3a, 3b and 3c). In these CyDs, a glucose residue has been replaced by an altro-pyranose unit with an axial hydroxyl group. Assignments were made with one-dimensional NMR and COSY, TOCSY, ROESY and CHSHF (heteronuclear shift correlation) spectra. Titration by NMR shift changes gave amino-group pK a values of 7.73 and 8.84 for 3b and 6A-amino-6A-deoxy-b-CyD (6b), respectively. Polymer Journal ( Keywords: altro-cyclodextrin; hydrogen bonding; NMR; structural assignment; titration INTRODUCTIONCarbohydrates are key recognition elements in biological processes. However, in most cases, the role of carbohydrates and the detailed mechanisms of these events are still poorly understood. It seems that a clear model of the structure of carbohydrates is very important for understanding the role of carbohydrates in these processes. Carbohydrates look much simpler than other biomolecules as they differ from each other mainly by stereochemistry. However, carbohydrates actually have much more information capacity than proteins because they vary by linkages and stereochemistry and can be branched. The structure determination of complex oligosaccharides involves discovering the primary structure, stereochemistry, sequence, linkages and anomeric configurations; thus, it is actually a very challenging problem.Cyclodextrins (CyDs) are naturally occurring cyclic carbohydrates consisting of 6-8 glucopyranosyl residues linked by a-1,4 glycosidic bonds. They have a hydrophobic cavity and form inclusion complexes with various guest molecules in aqueous solution and solid state.

Cyclodextrins 3‐Functionalized with 8‐Hydroxyquinolines: Copper‐Binding Ability and Inhibition of Synuclein Aggregation

“…The high stabilityo ft he M 2 Lc omplex formedb y4 is likely ascribable to the involvement of the deprotonated amide groups in metal coordination,a sp reviouslyf ound through ESI-MS. [13] In this case, the presence of two adjacent altroseu nits can disturb the hydrogen-bondingn etwork [30] and modify the rigidity of the cavity,a sr eportedf or other altro-cyclodextrin derivatives. [31] Unlike ligand 3,t he HQ moieties of 4 could act as tridentate ligands (amide and pyridine nitrogen atoms, phenolate oxygen atom) in the M 2 Ls pecies ( Figure S5).…”

Supramolecular Zn(II)-Dipicolylamine-Azobenzene-Aminocyclodextrin-ATP Complex: Design and ATP Recognition in Water

“…On the other hand, the increase in pH from 7.4 to 11.0 produced a decrease in the number of protonated amino groups of 3-NH 2 - γ -CyD. The correspondent p K a of 3-NH 2 -γ -CyD is reported to be 7.73 [ 33 ], and therefore, a similar value is expected for the 1-Zn /3-NH 2 - γ -CyD complex. Similarly to acidic conditions, the increase of pH to 11 produced a loss of electrical neutrality as well, resulting in a lower ICD spectral response.…”

Adjusting the Structure of β-Cyclodextrin to Improve Complexation of Anthraquinone-Derived Drugs

“…A pKa value of 4.5 means that, at a pH below the pKa value, the CD derivative is usually in protonated form, and its additional positive charge in the triazole ring may affect the strength of the drug binding with the CD derivatives. For the amine derivative CD, the pKa value is available in the literature, and its value equal to 8.84 [ 32 ] does not affect the strength of the binding of this cyclodextrin with the drug at the range of physiological pH we tested.…”