Novel approach to determining the absolute configurations at the C3-positions of various types of sterols based on an induced circular dichroism.

Circular dichroism (CD) spectra of the 2,2'-binaphthyl ester derived from Δ(5)-sterols showed not bisignate CD but diagnostic CD bands at around 210 and 240 nm. These bands might be attributable to an interaction between an olefinic chromophore and a binaphthyl one. Various types of unsaturated sterols were thus derivatized followed by complete hydrogenation, to give saturated sterols. As a result, CD spectra of the binaphthyl derivatives of the saturated sterols showed bisignate curves centered at 240 nm (3S(β): positive chirality; 3R(α): negative one). This suggested a straightforward and practical method for discriminating the absolute stereogenic center at the C-3 positions of sterols based on an induced CD. This finding should contribute significantly to the analysis of metabolites of various types of sterols.
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