Steric crowding and conformer stability of the diol-epoxides of benzo(c)phenanthrene.

The relative stabilities of conformers of the syn and anti-diastereomers of the fjord and bay-region diol-epoxides of benzo(c)phenanthrene (BCP) and benzo(a)anthracene (BA) have been calculated. Steric crowding in the fjord-region of BCP is shown to stabilize the syn-diequatorial and anti-diaxial conformers of BCP. In contrast, the most stable conformers of the bay-epoxides of BA are found to be the syn-diaxial and anti-diequatorial.