General formula of a mesylate ester structural formula of the mesylate anion
Mesylate is the trivial name for methanesulfonate, which indicates an ester or salt of methanesulfonic acid. Salts contain the mesylate anion CH3 SO3. Mesylate esters have the general structure CH3 SO2 O-R, where R is an organic radical. Mesylate is a good leaving group in nucleophilic substitution reactions.
In pharmaceuticals containing such a group or anion, the spelling mesilate is used in the International Nonproprietary Name (INN), for example imatinib mesilate for the methanone sulfonic acid of imatinib.
Mesylate esters can be prepared by reacting methanesulfonyl chloride with an alcohol in the presence of a base (usually triethylamine, in combination with 4-dimethylaminopyridine as nucleophilic catalyst):
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