Axially Chiral Dimeric Naphthalene and Naphthoquinone Metabolites, from Root Cultures of the West African LianaTriphyophyllum peltatum

Abstract

Root cultures of the West African liana Triphyophyllum peltatum were initiated from stem explants of in vitro cultivated shoots. From these organ cultures, three new binaphthalenes, one binaphthoquinone, and two (bi)naphthalene glucosides were isolated, with substitution patterns related to those of the naphthylisoquinoline alkaloids, which are the "normal" main metabolites of T. peltatum. The structures of the diglucoside dioncoquinoside A (1) and of the axially chiral biaryls triphyoquinols A1 (3), A2 (4), and B (5), triphyoquinoside A (6), and triphyoquinone A (7) were elucidated by spectroscopic analysis (HRESIMS, 1D and 2D NMR) and by application of electronic circular dichroism (ECD) spectroscopy in combination with the exciton chirality method and quantum-chemical ECD calculations. The root cultures likewise produced the known alkaloids dioncophylline A (8), 5'-O-demethyldioncophylline A (9), dioncopeltine A (10), habropetaline A (11), and 5'-O-methyldioncophylline D (12a/b), the naphthalene glucoside plumbaside A (2), and the naphthoquinones plumbagin (13), droserone (14), and 8-hydroxydroserone (15).

Transformation of Substituted Glycals to Chiral Fused Aromatic Cores via Annulative π-Extension Reactions with Arynes

“…Fused aromatic rings flanked by two sugar units are reported to serve in the defense mechanism of plants against herbivores. 6 We therefore thought of synthesizing their C-analogues using our methodology. Toward this, we prepared a chiral difunctionalized naphthalene glucoside derivative in a single step by subjecting substrate 4 (Scheme 3) to this reaction with a 3-methoxyaryne derived from 5.…”

“…Fused aromatic rings flanked by two sugar units are reported to serve in the defense mechanism of plants against herbivores . We therefore thought of synthesizing their C-analogues using our methodology.…”

Flavonostilbenes Isolated from the Stems of Rhamnoneuron balansae as Potential SIRT1 Activators

“…Compound 1 was found to have an axial chirality due to steric hindrance in the biaryl axis. Thus, the absolute configurations of dihydroflavonol and the biaryl axis were determined by electronic circular dichroism (ECD) analysis after confirming the purity of compound 1 using a Chiralpak IA column (250 × 4.6 mm i.d., 5 μm). − The conformational analysis of compound 1 was obtained by Conflex in the MMFF94s force field, and more than 1% of the conformers were used for ECD calculations. ECD calculations were performed at the B3LYP/DFT functional level with the basis set 6-31G for all atoms (Figure A).…”

Carnivory on demand: phosphorus deficiency induces glandular leaves in the African liana Triphyophyllum peltatum

“…Interest in Triphyophyllum peltatum , which is traditionally used in folk medicine (Porembski & Barthlott, 2003), is based on its rich production of pharmaceutically active secondary metabolites, namely acetogenic naphthoquinones (Bringmann et al ., 2016a), tetralones and structurally unique, axially chiral naphthylisoquinoline alkaloids (Bringmann et al ., 2000). Among these alkaloids, dioncopeltine A (François et al ., 1997), dioncophylline B (François et al ., 1999), dioncophylline C (François et al ., 1997) and habropetaline A (Bringmann et al ., 2003) have strong antiplasmodial activities (François et al ., 1997).…”

“…Under in vitro conditions, Bringmann & Rischer (2001) observed carnivorous glandular leaves only in exceptional cases on adventitious shoots regenerating from callus. Nevertheless, the possibility to establish in vitro cell (Bringmann et al ., 2016b) and root cultures (Bringmann et al ., 2016a) may help to preserve germplasm ex situ .…”