Studies on the syntheses of heterocyclic and natural compounds. Part 939: An efficient and stereoselective synthesis of des-a-ring steroids—potential intermediates to …
A stereoselective synthesis of des-A-ring steroids 9 and 17 has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2- one-2-ethylene ketal 7 and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol 16, respectively.