Total synthesis of both enantiomers of the macrocyclic lactone citreofuran.
Both enantiomers of the polyketide-derived lactone citreofuran (4) have been prepared. The enantiopure building blocks were obtained on a chemoenzymatic route ((S)-6) and by a chiral pool synthesis ((R)-6). The crucial step in the synthesis, a macrolactonization, was accomplished under Mitsunobu conditions.