Hi Anvish,

Convert your acid to acid chloride through reaction with thionylchloride (SOCl2) , then the product will react with alcohol very fast with high yield. good luck.

Thanks  a lot Salim Y Hanna !!

t-butanol is difficult to react due to the steric. Other than making the acid chloride, you may try reacting isobutene with the carboxylic acid in acidic conditions

Thanks Eugene !! Producing isobutene gas  in our case is bit difficult.. Can you suggest any  other idea !!

try esterification with mixed anhydride (isobutyl chloroformate or pivaloylchloride) and then add t-Butanol

Good day

I suggest to show the esterification method in my search, the diclofenac acid converted to acyl chloride through reaction with equimolar of SOCl2 in cooled environment

Thanks a lot Arun.. !! Will that possible to share any article. 

Thanks a lot Noor!! But we are looking for pyridine kind of moiety not for normal phenyl. Already tried didn't work !! 

The main problem with the Solubility Conpound is highly water soluble I even tried with dissolving in DCM with DMF, Can we use Trimethyl amine instead of DMF or Pyridine 

Trans-esterification with another t-butyl ester might be the best approach.  See link for one example.  The usual catalyst is an acid, but your quinoline might prevent you from generating a reasonable proton activity, unless you convert it to a salt with a full equivalent of acid.  These reactions probably proceed via an isobutylene intermediate.

http://www.sciencedirect.com/science/article/pii/S0040403906004539

Treat you acid with oxalyl chloride in DCM in presence of pyridine. You may warm it too. Once acid chloride is done (a small amt reacted with methanol to run TLC) treat with the alcohol you want it to esterify with to get the ester.

I did the same for a quinolone with a COOH in position 3. and gave moderate yields. Dissolve ur cpd in (In this case your Alcohol) MeOH then add dropwise Conc. H2SO4. then heat over night at 100C.

Hope it works :)

All the above methods are great. I am a fan of isobutylene gas and catalytic sulfuric acid in DCM. 

Also perchloric acid in tert-butyl acetate works well. These of course have less functional group/protecting group compatibilities.

I suggest to show the esertification method in my search,