Dioncopeltine A and dioncolactone A: Alkaloids from Triphyophyllum peltatum
摘要:
The isolation of two novel alkaloids from Triphyophyllum peltatum is described. The complete stereostructure of dioncopeltine A, which is closely related to dioncophylline A, is established by spectroscopic, chiroptical, and degradative methods, and is furthermore confirmed by its transformation to O-methyl-dioncopophylline A, as well as by X-ray crystallography. Dioncolactone A, which can be transformed into dioncopeltine A by reductive ring-opening, is the first naturally occurring representative of this novel type of 'axially prostereogenic' biaryl alkaloids.
5′-O-demethyl-8-O-methyl-7-epi-dioncophylline a and its ‘regularly’ configurated atropisomer from Triphyophyllum peltatum
摘要:
The isolation and structure elucidation of two new minor naphthylisoquinoline alkaloids from the stem bark of Triphyophyllum peltatum is described. From extended spectroscopic investigations, mainly NMR and CD spectroscopy, one of the alkaloids is deduced to be 5'-O-demethyl-8-O-methyl-7-epi-dioncophylline A. This new natural product is, thus, the first dioncophylline A analogous naphthylisoquinoline alkaloid from T. peltatum with an opposite configuration at the biaryl axis. Moreover, low amounts of an additional new alkaloid were isolated, whose spectral data suggest 5'-O-demethyl-8-O-methyl-dioncophylline A, i.e. the corresponding 'normal' atropodiastereomer.