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H. Kalaus, A. Reichetseder, C. Stanetty, M.D. Mihovilovic:
"Kinetic Quantification of Aldose Open-Chain Content";
Poster: XXth European Carbohydrate Symposium (EUROCARB2019), Leiden; 30.06.2019 - 04.07.2019; in: "EuroCarb2019 Poster abstracts", (2019), 291 S.

Within our research we aim to translate the ever-expanding repertoire of aldehyde-methodology chemistry to
Nature´s most prominent, yet, in most studies scorned, representatives: aldoses. In most sugars, the cyclic lactol
form dominates with only minute amounts being present as open-chain (aldehyde) species. Consequently, reactions
of sugars acting as aldehydes occur significantly slower than usual and side-reactions can become favored, thus in
the case of unstable reagents incomplete or complete lack of conversion can be observed.
So far, an efficient tool for the quantification of aldoses´ open chain-contents (OCC) was missing, with previously
established methods relying on NMR-analysis of [1-13C] enriched sugars [1] or long-time (up to years) kinetic
measurements [2].
Herein, we now demonstrate a photometric kinetic assay for the quantification of OCCs, exploiting the fast and
irreversible adduct-formation of aldehydes and 2-aminobenzoamidoxime [3]. The kinetic curves of the adduct
formation of all parent C4-C6 aldoses were determined, which suggested two separate families depending on the
relative 2,3-configuration (erythro and threo). The derived OCCs proved to be in consistence with literature data with
our approach significantly outperforming aforementioned methods in respect to reduced measurement times (hours)
and ease of operation. Furthermore, a first real case example will be presented; that of 2,3-isopropylidene protected
L-erythrose which did by no means undergo indium mediated acyloxyallylation in vast contrast to its unprotected
very reactive counterpart. Utilizing our assay, relative OCC and respective aldehyde reactivity could be deduced for
the unreactive species in a few straight-forward measurements [4].
The developed assay will prove a valuable tool in future projects, where the availability and reactivity of the aldehyde
moiety in sugar molecules has to be addressed.


1. Zhu, Y.; Zajicek, J.; Serianni, A. S., Acyclic Forms of [1-13C]Aldohexoses in Aqueous Solution: Quantitation by
13C NMR and Deuterium Isotope Effects on Tautomeric Equilibria. J. Org. Chem. 2001, 66 (19), 6244-6251.
2. Dworkin, J. P.; Miller, S. L., A kinetic estimate of the free aldehyde content of aldoses. Carbohydr. Res. 2000,
329 (2), 359-365.
3. Kitov, P. I.; Vinals, D. F.; Ng, S.; Tjhung, K. F.; Derda, R., Rapid, Hydrolytically Stable Modification of
Aldehyde-Terminated Proteins and Phage Libraries. J. Am. Chem. Soc. 2014, 136 (23), 8149-8152.
4. Draskovits, M.; Stanetty, C.; Baxendale, I. R.; Mihovilovic, M. D., Indium- and Zinc-Mediated Acyloxyallylation
of Protected and Unprotected Aldotetroses-Revealing a Pronounced Diastereodivergence and a Fundamental
Difference in the Performance of the Mediating Metal. J. Org. Chem. 2018, 83 (5), 2647-2659.

https://publik.tuwien.ac.at/files/publik_284218.pdf

Projektleitung Christian Stanetty:
Kontrollierter Zuckerabbau durch N-Heterocyclische Carbene