Preparation of methyl ester precursors of biologically active agents

This method enables scientists to easily convert biologically active carboxylic acids into their methyl esters ("pro-drugs" generally having improved ability to penetrate cell membranes) using only equipment commonly found in a biology laboratory. An ion-exchange resin is used to convert the acid into its salt, which is thereby sequestered on the resin. The addition of methyl iodide converts the salt to the ester, which has no affinity for the resin and is readily eluted. Evaporation of the liquid phase provides the pure methyl ester. The preparation in good chemical yields of methyl esters of bioactive agents in excellent purity and 10–20 mg quantities can be achieved using this method. The method can be completed in 1 day.