Azidotrimethylsilylation of carbohydrates (monosaccharides and disaccharides) has been achieved in high yields under Mitsunobu conditions. The azidation of carbohydrates is effected at 0 °C essentially only at the primary alcoholic position in mono, di- and triols in protected/unprotected glycosides, whereas the remaining secondary hydroxyl groups got silylated. Surprisingly, no azidation of the secondary hydroxyls was observed in all the carbohydrate substrates. Applications of the methodology for the synthesis of amino sugars, triazoles and azasugars are reported.
An Approach to the Site-Selective Deoxygenation of Hydroxy Groups Based on Catalytic Phosphoramidite Transfer
作者:Peter A. Jordan、Scott J. Miller
DOI:10.1002/anie.201109033
日期:2012.3.19
Selective: The deoxygenation of simple and complex natural products employing a readily synthesized phosphoramidite and tetrazole catalysts can be executed as a two‐step process, without the need to isolate intermediate deoxygenation precursors. Furthermore, a peptide‐based tetrazole catalyst controls the site selectivity of deoxyerythromycin synthesis (see scheme), thus overcoming the notorious challenges
选择性:使用易于合成的亚磷酰胺和四唑催化剂对简单和复杂的天然产物进行脱氧可以作为两步过程进行,无需分离中间脱氧前体。此外,基于肽的四唑催化剂控制脱氧红霉素合成的位点选择性(参见方案),从而克服了未受保护的红霉素 A 的臭名昭著的挑战。