Carbon‐13 nuclear magnetic resonance spectra. VIII—18α‐ and 18β‐glycyrrhetic acid derivatives

The 13C NMR data of six pairs of 18α/18β‐glycyrrhetic acid derivatives are presented. It is shown that the configuration at C‐18 can easily be recognized by inspecting the chemical shifts of several characteristic carbons, e.g. C‐12, C‐13, C‐18 and C‐28. The shifts of these carbons originated by the change of the D/E ring junction proved to be largely independent of the substitution at C‐3 and C‐20.