
TY  - JOUR
A1  - Riemann, I. 
A1  - Fessner, W.-D. 
A1  - Papadopoulos, M. A. 
A1  - Knorst, M. 
T1  - <emph type="2">C</emph>-Glycosides by Aqueous Condensation of &#946;-Dicarbonyl Compounds with Unprotected Sugars
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 2002
VL  - 55
IS  - 2
SP  - 147
EP  - 154
KW  - 
UR  - https://doi.org/10.1071/CH02012 
N2  - 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. 
ER  -

