Cyclization of 3,3;20,20-bis(ethylenedioxy)-C-nor-9,11-seco-5α-pregnane-9β,11-diol into 11-oxa-5α,17α-pregnane-3,20-dione
Abstract
On refluxing with a catalytic amount of toluene-p-sulphonic acid in acetone, 3,3;20,20-bis(ethyl-enedioxy)-C-nor-9,11-seco-5α-pregnane-9β,11-diol (1) cyclized to give 11-oxa-5α,17α-pregnane-3,20-dione (2), via the transient formation of a hemiacetal.