However, the most preferred method for the esterification or preparation of the amides resides in a ring opening reaction of a lactone compound (F) with an alcohol R 1 -H or an amine R 1 -H. In Method 2, Step 1 , the brominated lactone (D) or (D') is for example prepared by reacting the corresponding acid with an equimolar amount of bromine at ambient temperature in acetic acid as solvent.