The unexpected course of the reaction of steroid sapogenins with diacetoxyiodobenzene and BF3·Et2O in formic acid

The reaction of steroid sapogenins of both the 25R and 25S series with diacetoxyiodobenzene and BF3·Et2O in formic acid produced a mixture of an equatorial 23-formyloxysapogenin, a 16β,23:23,26-diepoxy-22-one and a bisnorcholanic lactone. The outcome of this reaction, that drastically differs from the same reaction in acetic acid, opens up new possibilities for the transformation of the side chain of steroid sapogenins.