Sugars: sweet tales from an aldehyde's perspective

Session: 
S7.3 Catalytic glycan transformations
Code: 
OL7.3.2
Location (hall): 
Galactose
Start/end time: 
Wednesday, July 3, 2019 - 12:00 to 12:15
Christian
Stanetty

Christian Stanetty1, Markus Draskovits1, Hubert Kalaus1, Alexander Reichetseder1, Marko Mihovilovic1

1TU Wien, Vienna, Austria

Our research focuses on the development of new synthetic methodology for the interconversion of abundant sugars to more exotic ones utilizing the natural reactivity of the aldehyde moiety. The open chain content generally represents a minute minority in reducing sugars’ equilibria (dominated by the hemiacetal forms), which is usually too small to be determined efficiently and/or accurately. To overcome this issue, we have developed an assay based on the adduct formation of a strongly UV-active aminal species which thereby translates the open chain proportion into a readily measurable reaction rate (see Figure 1, middle). [1] We have confirmed the validity of the approach measuring all parent hexoses and pentoses and exhibiting a high degree of consistency with literature data. 

Next, we went on to apply the assay to real cases from the field of indium mediated acyloxyallylation [2] (Figure 1, bottom) and our current study of the organocatalytic anomeric activation by N-heterocyclic carbenes (NHCs) which we are  developing into a controlled dehomologation methodology (Figure 1, top). [3] In both areas we have encountered unexpected reaction outcomes which could not be explained by the sole chemical vicinity of the aldehyde function but could be correlated to the differences in the ratios of available open chain content within relevant starting materials, intermediates and products.

Figure 1: Indirect determination of open chain content and questions addressed by the developed UV-assay

References: 
  1. Reichetseder, A; Kalaus, H. Stanetty, C.;* Mihovilovic, M. D; in preparation
  2. Draskovits, M.; Stanetty, C.;* Baxendale, I. R.; Mihovilovic, M. D; J. Org. Chem. 2018, 83 (5), 2647-2659.
  3. Draskovits, M.; Kalaus, H. Stanetty, C.;* Mihovilovic, M. D; submitted 2019

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