5.2.1. Preparation of synthetic esters

Esters can be synthesized according to the following standard procedure (Francke et al., 2000):

 

  1. Dissolve 10 mmol of the alcohol in 10 ml absolute pyridine.
  2. Add a catalytic amount (ca. 10 mg) of 4-dimethylamino pyridine to facilitate the planned reaction.
  3. Cool the solution in an ice bath.
  4. Stir the solution and add 1.1 equivalent of the acid chloride, dissolved in 10 ml hexane.
  5. Continue to stir the resulting mixture for one hour at room temperature.
  6. Quench the reaction by slowly adding 100 ml of aqueous sodium hydrogen carbonate while stirring the mixture.
  7. Extract the aqueous phase with two subsequent 20 ml portions of hexane.
  8. Wash the combined hexane solution with 30 ml portions of each diluted hydrochloric acid, aqueous sodium hydrogen carbonate, and brine.
  9. Dry the solution with anhydrous magnesium sulfate and remove the white material by filtration.
  10. Concentrate the clear solution under reduced pressure of Nitrogen.
  11. Chromatograph the resulting crude product on silica gel (Merck 60–200 mesh) using hexane/ethyl acetate 30:1 as the eluent.
  12. Check the purity of the final product and provide its structural proof, by GC/MS (see section 2.2.4.1.1) and other spectroscopic methods (e.g. nuclear magnetic resonance (NMR)) in consultation with a chemist.