Triphyophylline

The or-naphthylisoquinoline alkaloids triphyophylline, isotriphyophylline, N-methyltriphyophylline, 8-O-methyltetradehydrotriphyophylline, and triphyo-peltine [assigned the structure (9 R — H) (cf Vol. 7, p. 107)] and its 5 -0-methyl ether (9 R = Me) have been isolated from Dioncophyllum thollonii.23... 

The first asymmetric synthesis of a 7,1 linked alkaloid was that of (-)-dioncophylline A (8) (triphyophylline) which resulted in the revision of the initially proposed stereostructure (ref. 77). The synthesis utilised the intramolecular approach that was successful for the synthesis of racemic 8 (see Scheme 7) and began with the production of optically pure tetrahydroisoquinoline 79... 

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 first total synthesis of the trans configurated tetrahydroisoquinoline alkaloid triphyophylline (23), via the lactone intermediate 108, was accomplished (see Scheme 26) (69). The use of an ester type auxiliary bridge, as in 107, still offered several crucial advantages over the above mentioned ether type prefixation of the molecular moieties. 

This first synthesis of triphyophylline (23) confirms its relative trans configuration of the two secondary methyl groups. A synthesis of this main Triphyophyl-lum alkaloid in optically active form, which is supposed to establish the chirality at the biphenyl linkage as well as the entire absolute stereochemistry, is under investigation in the author s laboratory. 

The first naphthyl isoquinoline alkaloid to be synthesized in optically active form was ancistrocladine (1) itself, the most important and widespread of all the Ancistrocladus alkaloids (see Scheme 31). The effectivity of the ester bridge assisted aryl coupling method (as presented in Section V.D.) was demonstrated by the regioselective formation of the highly strained lactone 124, which— different from the corresponding triphyophylline precursor 108 (see Scheme... 

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