Guettardine,a possible biogenetic intermediate in the formation of corynanthe-cinchona alkaloids

The structure of guettardine 1, an indole alkaloid isolated from the bark of $\text{Guettarda heterosepala}$ (Rubiaceae), was determined from an analysis of its MS, ¹H and ¹³C NMR spectral data, and by a chemical correlation with dihydrocorynantheol 7. Guettardine 1 can be considered to be an intermediate between the Corynanthé and the cinchonamine groups of alkaloids which are precursors of quinine and its derivatives.