structure and conformation of steriodals

Abstract

In the previous chapter, the influence of the same additional ring on two different steroid nuclei (1,4?diene?3?one and 5?ene) was discussed. Here, we present the effects of three different additional rings on the 5?ene skeleton. The following table lists the pseudorotation parameter A and asymmetry parameters at the point of interest.

Table: Conformational Parameters

CompoundCon200neConSMOnConORTConTriAConTriBRing DA–55.1–34.7–35.7–56.1–56.6?C??8.50.76.89.910.0ConformationD?14??E14??E14??ED?14??ED?14??ERing E?C??7.82.5*31.739.038.8?C? (13–17)1.6*12.065.663.663.3?C??19.723.89.8*8.9*8.5*Conformation13,17?HC17?E20?E20?E20?E HC – Half?chair; E – Envelope; D – Distorted *Corresponds to the lowest value.

The E?ring adopts the following conformations in the respective structures:

Con200ne: 13,17?half?chair ConSMOn: 17?envelope Conessine: 20?envelope

We observe that in all the present compounds, the D?ring conformation is restricted to the 14??envelope region. Therefore, it appears that regardless of the conformation of the additional E?ring, the D?ring conformation remains locked near the 14??envelope region in the 5?ene steroidal skeleton.