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Vorträge und Posterpräsentationen (mit Tagungsband-Eintrag):

M. Draskovits, C. Stanetty, M.D. Mihovilovic:
"Diastereoselectivity and diastereodivergence in the acyloxyallylation of aldotetroses";
Poster: 17. Österreichische Chemietage 2017, Salzburg; 25.09.2017 - 28.09.2017; in: "17. Österreichische Chemietage 2017", (2017).



Kurzfassung englisch:
Carbohydrates are often referred to as the Natures biggest chiral pool. Anyhow, only a small set of standard sugars are readily available (commercially and synthetically). This leads to the restriction of methodology to these abundant sugars. We set out to investigate more straightforward routes to exotic sugars, to bring those more into the centre of attention and application. The indium mediated acyloxyallylation of aldoses, introduced by the Madsen group a decade ago is an elegant way for the two-carbon elongation of reducing sugars (upon ozonolysis). In this study, the standard D-pentoses and D-hexoses were used as starting materials, giving rise to heptoses and octoses, respectively. Isolation and identification of the obtained products tends to be troublesome. Therefore, only the main isomer was described thoroughly, which featured a formal Lyxo-addition to the anomeric carbon. Recently, we have developed this methodology into a straight forward access to L-glycero-D-manno heptose, starting from L-lyxose. In this course, the two other formed diastereomeres were also identified, elucidating the type of selectivity observed when applied to reducing sugars.2 To prove this selectivity to be general, we set out to engage in an in-depth methodological investigation. We considered the tetroses as suitable starting materials, as hexoses would be obtained as products, allowing unambiguous identification via available authentic samples. We found the diastereoselectivity to be of the same pattern as already known from the pentoses and hexoses. Furthermore, a pronounced diasterodivergence was observed in partly protected erythrose and threose. Next, we evaluated the effect of steric bulk in the reagent on the diastereoselectivity as well as the replacement of indium with cheap zinc. However, a complete loss of diastereoselectivity was observed, rendering this otherwise attractive modification useless.
As a synthetically valuable side-line, we could establish a short scalable protocol towards L-allose, representing a second example of an exotic sugar made more readily available via acyloxyallylation.


Elektronische Version der Publikation:
http://publik.tuwien.ac.at/files/publik_264390.pdf


Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.