Towards better syntheses of partially methylated carbohydrates?

Several glycans and pharmacologically relevant glycosides display partially methylated carbohydrates. This structural feature plays a key role in the recognition of glycans by their receptors, and contributes to the bioactivity of natural and synthetic glycosides. Therefore, partially methylated sugars are attractive synthetic targets. While tremendous advances have been achieved during the last decade in the catalytic site-selective modification of sugars and while cleaner methylation reagents have been developed, such transformations have yet to be transposed to the selective installation of methyl groups onto carbohydrates. In this short review, we give an overview of the reported synthetic strategies towards partially methylated glycosides. We also discuss how better protocols could stem from the recent developments in the fields of site-selective transformations of carbohydrates and cleaner methylation reagents.