Mesylate

In organosulfur chemistry, a mesylate is any salt or ester of methanesulfonic acid (CH₃SO₃H). In salts, the mesylate is present as the CH₃SO−3 anion. When modifying the international nonproprietary name of a pharmaceutical substance containing the group or anion, the spelling used is sometimes mesilate (as in imatinib mesilate, the mesylate salt of imatinib).

Mesylate esters are a group of organic compounds that share a common functional group with the general structure CH₃SO₂O−R, abbreviated MsO−R, where R is an organic substituent. Mesylate is considered a leaving group in nucleophilic substitution reactions.