Simaba cuspidata

In 1952, Haynes et al. (7) isolated an alkaloid from Pentaceras australis (Rutaceae) grown in Australia. This alkaloid, with the molecular formula C14H8N2O, was named canthin-6-one (1). Giesbrecht et al. (2) later isolated a new type of alkaloid, 3-methoxycanthin-2,6-one (2), from Simaba cuspidata of Brazil. Then Ohmoto and Koike (5) isolated... 

Methoxycanthin-6-one (19) has been isolated from the bark of Simaba cuspidata (2) and the stem bark of Simaba multiflora (41). From IR, UV, high-resolution MS (M at mlz 250.0735), and H-NMR (8 3.99, 3H, s), it was supported that 19 was a methoxycanthin-6-one. From the fact that there are two isolated pairs of vicinal protons (H-1 and H-2 H-4 and H-5) in the H-NMR spectrum, it is obvious that the methoxyl group does not exist in ring C or D. In addition, the lower field proton H-8 (8 8.13, H, d, J = 2 Hz) in ring A does not show ortho coupling. These findings led to determination of structure 19. 

Quassinoids.—An X-ray crystal analysis of the tetra-acetate of bruceine C (61) has confirmed the previously established structure and established the E configuration of the double bond in the ester side-chain. Bruceantinol, a potent antileukaemic compound, has been shown to be 4 -0-acetylbruceine C (62). Simaba cuspidata and Ailanthus grandis (Simaroubaceae) both yielded the same two quassinoids, 6a-tigloyloxychaparrinone (63) and the new 6a-tigloyloxy-chaparrin (64), A. excelsa contains excelsin (65), an ester of the known... 

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