highly stereoselective de-Bruyn–Ekenstein rearrangement/aldol condensation/intramolecular oxa-Michael cascade reaction of unprotected ketoses with ketones was elaborated. By the utilization of this new and operationally simple methodology an access to β-C-glycosides is given. Extremely matched and mismatched cases were observed by using with natural or unnatural proline in these cascade reactions.
A novel and efficient direct aldol condensation from ketones and aromatic aldehydes catalyzed by proline–TEA through a new pathway
作者:Jun-feng Wang、Meng Lei、Qin Li、Ze-mei Ge、Xin Wang、Run-tao Li
DOI:10.1016/j.tet.2009.04.052
日期:2009.6
aldol condensation from various ketones and a wide range of aldehydes was catalyzed by l-proline–TEA (triethylamine) in MeOH at room temperature, affording the corresponding (E)-α,β-unsaturated ketones in excellent yields. By using the method, some complicated (E)-α,β-unsaturated ketone C-glycosides were obtained from unmodified ketone C-glycosides and aldehydes. This reaction proceeds through a new
A convenient, one-step, synthesis of β-C-glycosidic ketones in aqueous media
作者:Filipe Rodrigues、Yves Canac、André Lubineau
DOI:10.1039/b006642g
日期:——
Condensation of pentane-2,4-dione with different unprotected sugars in alkaline aqueous media gave quantitatively in one step β-C-glycosidic ketones.
戊烷-2,4-二酮与不同的未保护糖在碱性水介质中缩合一步定量地得到β-C-糖苷酮。
C-Glycosides by Aqueous Condensation of β-Dicarbonyl Compounds with Unprotected Sugars
作者:I. Riemann、W.-D. Fessner、M. A. Papadopoulos、M. Knorst
DOI:10.1071/ch02012
日期:——
water, under mildly alkaline conditions, provides a�convenient and effective route to C-glycosidic ketones in high yields. Reactions usually proceed with high β`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
C-glucosyl, mannosyl and galactosyl 2-iodopropane, readily obtained from the corresponding C-glycosyl ketones, were coupled with (+)- or (−)-camphorsultam glyoxylic oxime ether with diastereoselectivity ranging from 70:30 to 80:20. C-glucosyl allothreonine was obtained by cleavage of the camphorsultam moiety.