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Structural formula of the mesylate anion
Ball-and-stick model of the mesylate anion

In chemistry, a mesylate is any salt or ester of methanesulfonic acid (CH3SO3H). In salts, the mesylate is present as the CH3SO3 anion. When modifying the International Nonproprietary Name of a pharmaceutical substance containing the group or anion, the correct spelling is mesilate (as in imatinib mesilate, the mesylate salt of imatinib).[1]

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 an excellent leaving group in nucleophilic substitution reactions.

Mesyl is the term for the methanesulfonyl or CH3SO2− (Ms–) functional group. For example, methanesulfonyl chloride is often referred to as mesyl chloride.


Mesylates may be prepared using an alcohol and methanesulfonyl chloride in the presence of a base, often amine bases such as triethylamine.[2] Mesylates can also be prepared by combining an alcohol, methanesulfonic anhydride and base, although this method is generally used only if the nucleophilicity of chloride is a concern.

See also[edit]


  1. ^ World Health Organization (February 2006). "International Nonproprietary Names Modified". INN Working Document 05.167/3. WHO.  Retrieved 5 December 2008.
  2. ^ Rick L. Danheiser, Yeun-Min Tsai, and David M. Fink (1993), "A General Method for the Synthesis of Allenylsilanes: 1-Methyl-1-(trimethylsilyl)allene", Org. Synth. ; Coll. Vol. 8: 471  (a procedure illustrating the use of mesylates)