LONG-RANGE INTERACTIONS OF SUBSTITUENTS IN STEROIDAL MOLECULES

The dependence of the long-range electronic interactions of carbonyl g roups in alicyclic steroidal ring systems on (i) the basic ring struct ure (i.e., sterane vs. perhydrochrysene) and (ii) the position of subs titutents (i.e., combinations of the 2-, 3-, and 4-positions in ring A with the 15-, 16-, and I7-positions in ring D of sterane and the 15-, 16-, 17-, and 17a-positions in ring D of perhydrochrysene) was studie d using the MNDO algorithm. Ab initio variants were also performed for the parent hydrocarbon, 5 alpha-androstane. The variants consisted of both full optimization using an STO-3G basis set (Int. J. Quantum Che m. 41, 815 (1992)) and a partial optimization, C-C bonds only, using a 3-21G basis set. Results indicate that(i)the compounds with one subst ituent in the 3-position are the most stable and (ii) long-range inter actions, expressed as the participation of distant oxygen orbitals in the same lone-pair Mos, are large in all perhydrochrysene derivatives and significant in all sterane derivatives, 3,I7-steranedione excepted . (C) 1993 John Wiley & Sons, Inc.