Structural and synthetic studies of alkaloids of the Proteaceae

Following the discovery of the presence of alkaloids in an endemic Tasmanian Proteaceous species, Bellendena montana R.BR., a detailed phytochemical examination for alkaloids has been undertaken. In addition, three other species of the Proteaceae, Darlingia darlingiana (F. MUELL) L.A.S. JOHNSON, Darlingia ferruginea, J.F. BAILEY, and Agastachys odorata R.BR., also found to contain alkaloids, have been subjected to a similar examination. This study has resulted in the isolation of fifteen alkaloids, of which twelve have been structurally identified by spectroscopy and synthesis. The structures of the bases have been shown to be derivatives of the tropane class; eight alkaloids with novel structures have been classified in two new tropane categories, those of y-pyronotropanes and 2-benzoyl tropanes. Use has been made of proton magnetic resonance and carbon magnetic resonance spectroscopy in determining relative stereochemistries of the bases, and a discussion of the 13C N.M.R. of y-pyrones is given. Two stereochemical series of tropane diol esters have been prepared and the spectroscopic data relating to these bases are presented. A general synthetic procedure has been developed to apply to the y-pyronotropanes; each of the naturally occurring alkaloids has been synthesized by a condensation between tropan-3-one and an enol ether derivative of a β-keto acid chloride. The probable biogenetic relationships between the alkaloids of the species under study and those recently described, of Knightia deplanchei VIEILL. ex BROGN et GRIS (Proteaceae) are described in terms of a biosynthesis from ornithine and a polyketide chain terminated with a non-acetate moiety