Efficient Photoinduced alfa-Deoxygenation of aldonolactones

C. MARINO; A. BORDONI; R. M. DE LEDERKREMER

Whistler; Canada,

Congreso; XXIII International Carbohydrate Symposium.; 2006

National Research Council Canada and Simon Fraser University

The development of specific deoxygenation methods for sugars is important for the preparation of many biological important sugars from readily available precursors. Among a variety of methods for carbohydrate deoxygenation, tin radical cleavage of thiono esters developed by Barton and McCombie has been widely used [1]. However, avoiding the use of reagents such as tri-nbutyl hydride and thiocarbonyl reagents is desiderable from the environmental and economic point of view. In connection with our project on the development of synthetic tools for the galactofuranose glycobiology, we have developed strategies for the synthesis of deoxygenated galactofuranosides in order to stablish the importance of each hydroxyl group in the interaction with the galactofuranosidase [2-4]. For the synthesis of 2-deoxy-D-lyxo-hexofuranosides (2-deoxy-galactofuranosides), we started from D-galactono-1,4-lactone, and the deoxygenation step was performed via a photoinduced electron transfer (PET) reaction on compound 1, using 9-methylcarbazole (MCZ) as photosensitizer [4]. Surprisingly, the reaction conditions necessary for the deoxygenation of compound 1 were extremely mild in comparison with the required for not carbonyl compounds. The effectiveness of this reaction on lactone derivatives, should be due to the stabilization that the carbonyl group produces on the intermediate radical.