Methylation is the reaction in which Methyl group is added to a compound by utilizing different reactions. In biological compounds like DNA, Methyl group is often added to Nitrogenous bases so that the activity can be changed.
In methylation of sugars, the hydroxyl groups are converted into ethers by reacting sugars with Methyl Halides, specially Methyl Iodides (very reactive due to good leaving group i.e Iodide).
Hydrolysis of disaccharides yields two monomers.
Following reaction shows the methylation of sucrose, followed by Hydrolysis.