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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… Click to show full abstract
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 CF3SO3H 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.
Journal Title: Organic letters
Year Published: 2019
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