Triphyophyllum alkaloids

Beside the Ancistrocladaceae, only one other plant family so far has been found to produce naphthyl isoquinoline alkaloids (see also Section IV,B), the Dionchophyllaceae (31-33). Triphyophyllum peltatum (Hutch, et Dalz.) Airy Shaw is a large liana (34), endemic to the rain forests of West Africa. From the twigs of this plant, Bruneton and Cave isolated a new alkaloid, named tri-phyophylline (57), which, in contrast to all kno n Ancistrocladus alkaloids (see Section II), has only one oxygen function on the isoquinoline part of the molecule. No degradation reactions have been described for any of the Triphyophyllum alkaloids. Based exclusively on spectral evidence, triphyophylline was assigned the structure 23 (see Table II). The stereochemistry of the two... 

A possible biosynthesis of the structurally related Triphyophyllum alkaloids fits impressingly well into this concept. Their lack of an oxygen function at C-6 perfectly corresponds to a joint biogenesis of both molecular halves of 29 from the same, less oxygenated diketone 32—a remarkably economical, converging biosynthesis which, despite the structural diversity of the two molecular moieties 34 and 35, manages with only the one monocyclic precursor 32. 

Further aldol condensation of the diketone 32 with methanolic KOH quantitatively gave the naphthalene 34, which was O-methylated to the dimethyl ether 74 (Scheme 15), the isocyclic molecular moiety of most of the Ancistrocladus and Triphyophyllum alkaloids (36,54,55). 

Scheme 17. Synthesis of the isoquinoline part of the Triphyophyllum alkaloid 29.

Bringmann, G., Holenz, J., Assi, L. A., Zhao, C. and Hostettmann, K. 1996. Molluscicidal activity of naphthylisoquinoline alkaloids from Triphyophyllum and Ancistrocladus species. Planta Medica, 61 556-557. 

Chiral 4 may be easily transformed into (—)-dioncophylline A (5)1 whose structure was elucidated recently1,3-6, a naphthalenylisoquinoline alkaloid from the carnivorous tropical liana Triphyophyllum peltatum. 

Naphthyl Isoquinoline Alkaloids from Triphyophyllum and Dionchophyllum Plants... 

Apart from this preliminary report, Triphyophyllum peltatum and Dioncho-phyllum tholonii are the only species outside the Ancistrocladaceae that contain naphthyl isoquinoline alkaloids. The characteristic biochemical difference, that... 

The identification of plumbagine (42), however, in Triphyophyllum peltatum 31), as well as in Ancistrocladus abbreviatus Airy Shaw 46), co-occurring with the alkaloids, can be interpreted as a strong indirect indication of a polyacetate pathway in the plants. By 1972, Zenk and co-workers had already found that the naphthoquinone 42 is formed from acetate units, albeit in Drosera and Plumbago species 47). A joint biosynthesis of plumbagine (42) and both molecular moieties, for example, of the alkaloid 23 from the same monocyclic precursor 32 seems evident (Scheme 6). 

T. Frosch, M. Schmitt, J. Popp, Ultrasensitive in situ tracing of the alkaloid dioncophyUine A in the tropical liana Triphyophyllum peltatum by applying deep-UV resonance Raman microscopy. Anal. Chem. 79, 986-993 (2007)... 

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