Methyl and Phenyl Glycosides of the Common Sugars

Abstract

This chapter discusses the methyl and phenyl glycosides of the common sugars. Several new general methods or modified procedures for glycoside synthesis have been introduced. The O -acylglycosyl halides, where the acyl group at the potential reducing group in a fully acylated reducing sugar has been replaced by halogen, are the most generally useful intermediates in the synthesis of alkyl and aryl glycosides, and the O -acetylglycosyl bromides (“acetobromosugars”) are by far the most commonly employed. They are more reactive than the chlorides and more stable than the iodides. In some instances, however, the bromide is so unstable that the chloride is preferred. Yields of O -acetylglycosyl bromides obtained from other sugars by this method were: lactose 85%, arabinose 50%, maltose 60%, cellobiose 72%, and galactose 75%. With cellobiose, some glacial acetic acid has to be added at the start to maintain solution. In general, the products are pure enough to be used without recrystallization in the next stage of glycoside synthesis. Apart from their use as starting materials for the preparation of O -acetyl-glycosyl halides, polyacetylated sugars are employed extensively in glycoside synthesis by the Helferich reaction, in which they are condensed directly with low-melting phenols.