Tetracyclic triterpenes. Part 7. Circular dichroism of some steroid and triterpenoid 5-en-7-ones; conformational aspects
Abstract
C.d. spectra of some steroid and triterpenoid 4,4-dimethyl-5-en-7-ones, showing long-wavelength n→π* and π→π* Cotton effects of opposite sign to those of ordinary 5-en-7-ones, are indicative of ring B conformations close to the two different sofa conformations: S(9α) in the 9α, 10β-series and S(8α) in the 9β, 10α-series.