Circulardichroismus—III : Die an C-9 und C-10 stereoisomeren 19-nor-5β-methyl-cholestan-3 und 6-ketone

Abstract

the circular dichroism of 3- and 6-keto steroids steroisomeric at C-9 and C-10 is related to their configuration and conformation, and the modification of the amplitude and even of the sign fo the Cotton effect by different substituents in position 6 and 3, resp., is discussed. The stereochemistry at C-9 can not be deduced from the circular dichroism of the 3-ketones, but from that of the 6-ketones; with the latter a constant shift of the ellipticity is found by epimerization in position 9 or 10. The 3,6-diketones of the A/B- cis-series show a pronounced vicinal effect of the CO groups, the dichrograms of the A/B- trans compounds, however, can be obtained by superposing the curves of the monoketones. Δ 9- and Δ 9(11)-19-nor-5β-methyl-cholestene ketones show similar Cotton effects as the corresponding saturated compounds with 9α,10β-configuration, the Δ 1(10) double bound, however, strongly influences the CO chromophores. With 9α,10β-Δ 1-en-3-ketones the fine structure of the Cotton effect is more characteristic for the stereochemistry at C-5 than its magnitude.