Brønsted acid-catalyzed dehydrative glycosylation reactions of 1-hydroxy sugars with alcohols are one of the most important and efficient reactions to prepare glycosides. Although the reaction is known as Fischer glycosidation reaction, scope of substrates is not necessarily wide because it requires excess amounts of alcohols.

We have recently reported DBSA (dodecylbenzenesulfonic acid)-catalyzed dehydration reactions in water. To expand the utility and the applicability of the work, we have developed DBSA-catalyzed dehydrative glycosylation in water. For example, O-benzyl protected furanose and pyranose reacted with 1-dodecanol in water to afford the desired products in moderate to high yields. In this case, protection of hydroxy groups is necessary to make sugars hydrophobic. In order to develop a more efficient process, we next focused on dehydrative glycosylation using free sugars. As a result, it was found that free sugars reacted with alcohols by using fluorous Brønsted acids in fluorous solvents. The detailed conditions, scope and limitation of both glycosylation processes will be discussed.