Unusual cyclization of 3,20-bisethylenedioxy-9,11-seco-C-nor-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 3,20-bisethylenedioxy-9,11-seco-C-nor-5α-pregnane-9β,11-diol (1) cyclized to give 11-oxa-5α,17α-pregnane-3,20-diene (2), via the transient formation of a hemiacetal.