Constituents of Naucleadiderrichii. Part VII. Synthesis of nauclederine, naucleonine, and naucleonidine; spectroscopic evidence for the structures of 3α-dihydrocadambine and two other constituents
Evidence is advanced concerning the structures of 6 N. diderrichii alkaloids, based on synthetic and spectroscopic studies. The synthesis of nauclederine, 2, provided support for the structural assignment made earlier. Synthesis showed that the structures previously assigned to the alkaloids designated ND-305B and ND-363C were incorrect; this led to revised structures for these alkaloids, now named naucleonine and naucleonidine, respectively, and these were established by synthesis. A tentative proposal was made for the structure of another constituent of the plant, designated ND-363B. Spectroscopic studies showed structure to be advanced for the glycosidic alkaloid, which was identical with the alkaloid 3.alpha.-dihydrocadambine obtained by Brown and Fraser.