O-Methylptelefolonium salt

Stem and branches of P. trifoliata but O-methylptelefolonium salt (36), shown previously to be the major quaternary component of the leaves, and the new alkaloid... 

An optically active alkaloid, ptelefolone, isolated from P. trifoliata, was shown by spectroscopic methods to be the 4-quinolone 82 (72) extraction of the flowers of this species yielded the analogous compound ptele-folidone (83) (56). The metho salt of ptelefolone, O-methylptelefolonium salt (84), is reported to be the major quaternary salt of the leaves of P. 

The approach used depends on the selective dehydration of hydroxy-isopropyldihydrofuroquinolines to produce terminal olefins. Acid-catalyzed dehydration resulted in the exclusive formation of the more stable isopropylfuroquinolines, e.g. 95. Although other conventional procedures were also largely unsuccessful, reaction of the hydroxy-isopropyldihydrofuroquinoline 93 with thionyl chloride and pyridine gave the terminal olefin 94, which was converted into O-methylptelefolonium salt (84). Triphenylphosphite dihalides in the presence of base, however, proved to be effective reagents. Thus, the phosphite dibromide and potassium carbonate reacted with platydesmine to give olefin 97 predominantly, which was converted into dubinidine (87) by treatment with osmium tetroxide. Ptelefolone was the only product formed when the 6,8-dimethoxy-4-quinolone 92 was treated successively with triphenylphosphite dichloride and with pyridine. 

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