Nukuhivensiums, indolo[2,3-a]quinoliziniums from the marquesan plant rauvolfia nukuhivensis

The first phytochemical inspection of the Marquesan endemic plant Rauvolfia nukuhivensis led to the isolation and structure characterization of two new indolo[2,3-a]quinolizinium derivatives named nukuhivensium (1) and N ₁₂-methyl-nukuhivensium (2). They feature an aromatic indolo[2,3-a]quinolizinium core, substituted at C-2 by a n-propyl group, which is unusual in this family of alkaloid derivatives. The structure elucidation was performed on the basis of NMR spectroscopy and especially by interpretation of 2D HMBC correlations. A biosynthetic pathway is proposed on the basis of known enzymatic transformations for this family of natural products. These compounds exhibited low antimicrobial activities.