Synthesis of two analogues of brassinolide, possible plant growth promoting steroids

The synthesis of two isomeric brassinosteroids, analogues of brassinolide, containing the 2β,3β diol system typical of ecdysteroids and a five-membered lactone bonded to the steroid ring B is described. The synthesis leads to both lactones via a metal hydride reduction of the Diels-Alder adduct of ergosterol.