Key Laboratory of Applied Surface and Colloid Chemistry , Ministry of Education , Xi'an , Shaanxi 710119 , P. R. China.
School of Chemistry and Chemical Engineering , Shaanxi Normal University , Xi'an , Shaanxi 710119 , P. R. China.
Org Lett. 2019 Feb 15;21(4):1103-1107. doi: 10.1021/acs.orglett.9b00009. Epub 2019 Feb 4.
An acidity- and temperature-dependent chemoselective glycosylation of silyl-protected rhamnals with alcohols has been revealed. The reaction undergoes a 1,2-addition pathway with (±)-CSA as the catalyst at rt, affording kinetically controlled 2-deoxyl rhamnosides. In contrast, only thermodynamically controlled 2,3-unsaturated rhamnosides are formed via Ferrier rearrangement when elevating reaction temperature to 85 °C or using CFSOH instead. This tunable glycosylation allows facile and practical access to both 2-deoxyl and 2,3-unsaturated rhamnosides with excellent yields and high α-stereoselectivity.
揭示了硅基保护的鼠李糖与醇在酸和温度依赖条件下的选择性糖苷化反应。在室温下，该反应以（±）-CSA 作为催化剂经历 1,2-加成途径，生成动力学控制的 2-脱氧鼠李糖苷。相比之下，当升高反应温度至 85°C 或使用 CFSOH 时，通过 Ferrier 重排仅形成热力学控制的 2,3-不饱和鼠李糖苷。这种可调的糖苷化反应可以方便、实用地以优异的收率和高的α-立体选择性获得 2-脱氧和 2,3-不饱和鼠李糖苷。
