원문정보
초록
영어
Previously, we reported an efficient one-pot direct glycosylation method with anomeric hydroxy sugars as glycosyl donors and phthalic anhydride and Tf₂O as activating agents. Although this method is very efficient for the selective β-mannosylation and other glycosylations, in certain cases, undesired self-condensed esters were generated as minor products. In order to suppress the generation of the self-condensed ester, 4,5-dimethoxyphthalic anhydride, 2,3-pyridinedicarboxylic anhydride, 3,4-pyridinedicarboxylic anhydride, and 4-methylphthalic anhydride were examined as activating agents instead of phthalic anhydride. 2,3-Pyridinedicarboxylic anhydride provided the best result and the improved glycosylation was carried out in three steps (ⅰ) the reaction of anomeric hydroxy sugars with 2,3-pyridinedicarboxylic anhydride in the presence of DBU at room temperature, (ⅱ) addition of Tf₂O at -40 ℃, and (ⅲ) addition of glycosyl acceptors to the reaction mixture at -40 ℃.