13C‐NMR. Analysis of the Roxburghines

Abstract
The13C shifts of the alkaloids roxburghine B, C, D and E are determined. They confirm the following configurations for the last three bases: C(18α)‐normal, C(18α)‐pseudoand C(18β)‐pseudo, respectively. Roxburghine B is shown to be a C(18β)‐epi‐alloisomer.