Scientific publications
Armelle Tontsa Tsamo* (Corresponding author)
Other affiliations: Tshwane University of Technology · University of Göttingen
Julio Issah Mawouma Pagna
Pamela Kemda Nangmo
Other affiliations: Institut de Recherches Médicales et d’Etudes des Plantes Médicinales
Augustin Ephrem Nkengfack
Hartmut Laatsch
Zeitschrift für Naturforschung C
Three new limonoids, designated as rubescins F (1), G (2), and H (3), together with two known compounds of this type, TS1 (4) and trichirubine A (5), were isolated from methylene chloride/methanol extracts of Trichilia rubescens leaves. The structures of these compounds were elucidated based on 1D and 2D nuclear magnetic resonance (NMR) analysis and complemented by electrospray ionization high-resolution mass spectrometry results and by comparison to data of related compounds described in the literature and ab initio calculations. Rubescin F (1) is the first limonoid from Trichilia spp. with an oxetane ring between C-7 and C-14, which seems to be formed by the isomerization of TS1 (4). The γ-hydroxybutenolide rubescin G (2) is a potential precursor of trichirubine A (5), whereas rubescin H (3) is the first example of a triterpenoid with a single bond between C-7/C-14, forming a cyclopropane ring. The absolute configuration of these limonoids was derived from biosynthetic considerations and ab initio calculations of NMR and optical rotation dispersion data.
