Could you protect the carboxyl group as a benzyl ester (see Esterification of carboxylic acids by benzyl chloride using quaternary ammonium salts Jihad Dakka,   Yoel Sasson,   Kamal Khawaled,   Georges Bram and   André Loupy   

J. Chem. Soc., Chem. Commun., 1991, 853-854) and then do the acetylation with acetic Anhydride and TEA and then hydrogenate to cleave the benzyl ester? When the carboxylic acid is protected it cannot interfere with the acetylation.

I disagree with Talaat. Acetic anhydride may well facilitate an intramolecular esterification reaction (lactone formation). If the carboxylic acid reacts with the anhydride first, forming a mixed anhydride, then intramolecular attack of the alcohol on the mixed anhydride could well result in a lactone.

You can protect the carboxylic acid as suggested by Matthew, but it might be better to change the experimental procedure before adding potentially unnecessary steps to a synthesis.

It is possible that you can get better selectivity from slow addition of the alcohol to a premixed solution of the anhydride, TEA and catalyst (like N-methylimidazole, DMAP or DMF). If that doesn't work, try the same thing, but with the acid chloride instead of the anhydride.

Good luck!

Esters are made by the condensation reaction between a carboxylic acid and an alcohol. The reaction is acid catalyzed. So you can use acetic acid and condense it with alcohol. Same as shown below.. If you really need to use anyhdride you may try adding NaH or other base then displace Na with Ac2O usually carboxylates should not react. 

it may go by first wth protection of acid group as a methyl ester(means meI+k2co3+h2o) then after with acetic anhydride to acylate.