化学
Knoevenagel冷凝
绿色化学
分子内力
有机化学
另一个
生物催化
离子液体
糖基
糖苷
糖苷键
水溶液
立体选择性
催化作用
药物化学
酶
作者
Ingo Riemann,Michael A. Papadopoulos,Marion Knorst,Wolf‐Dieter Fessner
摘要
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 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 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.
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