Long-range interactions of substituents in steroidal molecules



The dependence of the long-range electronic interactions of carbonyl groups in alicyclic steroidal ring systems on (i) the basic ring structure (i.e., sterane vs. perhydrochrysene) and (ii) the position of substitutents (i.e., combinations of the 2-, 3-, and 4-positions in ring A with the 15-, 16-, and 17-positions in ring D of sterane and the 15-, 16-, 17-, and 17a-positions in ring D of perhydrochrysene) was studied using the MNDO algorithm. Ab initio variants were also performed for the parent hydrocarbon, 5α-androstane. The variants consisted of both full optimization using an STO-3G basis set (Int. J. Quantum Chem. 41, 815 (1992)) and a partial optimization, C[BOND];C bonds only, using a 3-21G basis set. Results indicate that (i) the compounds with one substituent in the 3-position are the most stable and (ii) long-range interactions, 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, 17-steranedione excepted. © 1993 John Wiley & Sons, Inc.