
%0 Journal Article
%A Riemann, I. 
%A Fessner, W.-D. 
%A Papadopoulos, M. A. 
%A Knorst, M. 
%T <emph type="2">C</emph>-Glycosides by Aqueous Condensation of &#946;-Dicarbonyl Compounds with Unprotected Sugars
%J Australian Journal of Chemistry
%D 2002/06/04
%V 55
%N 2
%P 147-154
%K 
%R https://doi.org/10.1071/CH02012
%U https://www.publish.csiro.au/paper/CH02012 
%X Condensation of 1,3-diketones with unprotected aldoses in water, under mildly alkaline conditions, provides a convenient and effective route to C-glycosidic ketones in high yields. Reactions usually proceed with high &#946;`anomeric' stereoselectivity because product composition is determined by thermodynamic control. Mechanistically, the condensation follows a typical Knoevenagel scheme, after which an intramolecular oxa-Michael cyclization determines C-glycoside configuration by following an exo- or endo-trig pathway. With open-chain 1,3-diketones, an ensuing retro-Claisen fragmentation occurs to furnish simple glycosyl monoketones. The C-glycosides then slowly further dehydrate under the reaction conditions to give 2,5-disubstituted furans. 
