Prenyl-quinolones and Related Tricyclic Alkaloids

Kaneko, T. Naito, M. Hashiba, H. Fujii, and M. Somei, Chem. Pharm. Bull., 1979, 27, 1813. 

Reagents i, cone. HC1, heat ii, HC02H, at 90 °C iii, Mel, K2C03, Me2CO iv, DDQ, reflux in PhH v, HC104, heat 

A full account has been published of the synthesis of O-methylptelefolonium iodide (14) (cf. Vol. 9, p. 84) and of ( )-dubinidine (15) (cf. Vol. 3, p. 107) only a single diastereoisomer of dubinidine was obtained in the synthesis.19 

The first dimeric quinoline alkaloid, pteledimerine, was isolated recently from the root bark of Ptelea trifoliata (cf. Vol. 10, p. 80). Several related compounds have now been found in the same species, and the structure of one of them, pteledimeridine (16), was elucidated mainly by means of H n.m.r. and mass spectroscopy.9 The two dimeric alkaloids are isomeric and differ only in the nature of the furoquinolone portion, which has angular annelation (2-quinolone) in pteledimeridine and linear annelation (4-quinolone) in pteledimerine. 

3-Prenyl-quinolones and Related Tricyclic Alkaloids.— The 3-prenyl-2-quinolone preskimmianine (19), first obtained from Dictamnus albus, has now been recognized as a constituent of D. angustifolius. The 3-prenyl-2-quinolone 

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Prenyl-quinolones and Related Tricyclic Alkaloids.—The l-methyI-3-prenyl-2-quinolone (6 R1 = H, R2 = OMe), already known as a synthetic compound, has been isolated from the roots of Glycosmis mauritiana it is converted into a mixture of the dihydropyrano-quinolones (8 R1 = H, R2 = OMe) and (9 R1 = H, R2 = OMe) by formic acid (Scheme 2).4 A new l-methyl-3-prenyl-2-quinolone, 7V-methylpreskimmianine (6 R1 = R2 = OMe), was obtained from the stem bark of Vepris louisii-, its structure was established by spectroscopy and by its preparation from preskimmianine (7) (Scheme 2).11 A second new alkaloid of Vepris louisii, named veprisine, was shown by spectroscopic studies and by its synthesis from A-methylpreskimmianine to be the pyrano-quinolone (10) (Scheme 2).11 Five furoquinoline alkaloids were found in the wood of Esenbeckia flava (see Table 1) and a non-crystalline bisprenyl compound (11) was also isolated from this source the new alkaloid, which was first obtained as a synthetic compound,17 is readily converted into the dihydropyrano-4-quinolone (9 R1 = R2 = H) (Scheme 2).1... 

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