5.2.1. Preparation of synthetic esters
Esters can be synthesized according to the following standard procedure (Francke et al., 2000):
- Dissolve 10 mmol of the alcohol in 10 ml absolute pyridine.
- Add a catalytic amount (ca. 10 mg) of 4-dimethylamino pyridine to facilitate the planned reaction.
- Cool the solution in an ice bath.
- Stir the solution and add 1.1 equivalent of the acid chloride, dissolved in 10 ml hexane.
- Continue to stir the resulting mixture for one hour at room temperature.
- Quench the reaction by slowly adding 100 ml of aqueous sodium hydrogen carbonate while stirring the mixture.
- Extract the aqueous phase with two subsequent 20 ml portions of hexane.
- Wash the combined hexane solution with 30 ml portions of each diluted hydrochloric acid, aqueous sodium hydrogen carbonate, and brine.
- Dry the solution with anhydrous magnesium sulfate and remove the white material by filtration.
- Concentrate the clear solution under reduced pressure of Nitrogen.
- Chromatograph the resulting crude product on silica gel (Merck 60–200 mesh) using hexane/ethyl acetate 30:1 as the eluent.
- Check the purity of the final product and provide its structural proof, by GC/MS (see section 188.8.131.52.1) and other spectroscopic methods (e.g. nuclear magnetic resonance (NMR)) in consultation with a chemist.