Total synthesis of 14β-fluorosteroids via a transannular DielsAlder reaction

14β-Fluorosteroids 3 and 4 were synthesized to give a new class of unnatural cardenolides. The total synthesis of racemic 14β-fluorosteroids was accomplished using a highly diastereoselective transannular Diels–Alder reaction on a trans-cis-cis macrocyclic triene. The α-fluoro analog 4 provided a comparable inhibitory activity to natural digitoxigenin 1.Key words: fluorosteroid, bioisostere, cardiovascular diseases, transannular Diels–Alder reaction (TADA), macrocyclization.