Electronic structure and long-range interaction in androstanes

• Published in: Computers & chemistry 1990, Vol.14 (4), p.287-294
• Main Authors: Klasinc, L., Tolić, Lj.Paša, Spiegl, H., Knop, J.V., McGlynn, S.P.
• Format: Article
• Language: English
• ISSN: 0097-8485
• DOI: 10.1016/0097-8485(90)80034-Y

The results of semiempirical MNDO calculations with full geometry optimization are reported for 5α-androstane, 5α-androstan-3-one, 5α-androstan-11-one, 5α-androstan-16-one, 5α-androstan-17-one, 5α-androstane-3,16-dione, 5α-androstane-3,17-dione, 5α-androstane-3,11,17-trione, and five of its unsaturated keto derivatives: androst-5-en-17-one, androst-4-ene-3,16-dione, androst-4-ene-3,17-dione, androst-5-ene-3,17-dione and androsta-1,4-diene-3,17-dione. Emphasis is placed on the long-range effects of carbonyl group(s) located at the biologically important 3-, 11- and/or 17-positions, and on the dependence of these effects on the presence of interpolated localized double bonds. The effects of placing the carbonyl group in the 16- rather than the 17-position were studied and it was found that the former location produced a more efficient mixing of longitudinal and transversal ribbon-like σ-orbitals of the steroidal skeleton and, hence, enhanced the long-range coupling with substituents in the 3-position. Such long-range effects seem to exert considerable influence on conformation and activity, and, particularly, on the fast intramolecular electron transfer that has been observed recently in steroid solutions.