- Quinoline alkaloids: Synthesis of pyrano[2,3,-b]quinolines, khaplofoline, lunacrine, and demethoxylunacrine
-
Polyphosphoric acid (PPA)-catalyzed cyclization of 2-ono-3- vinylquinolinecarboxylic acid (1) yielded 3,4-dihydro-2,2-dimethyl-2H- pyrano[2,3-b]quinoline (4). The same reaction of 4-methoxy-2-oxo-3- vinylquinolinecarboxylic acid (1g) afforded 4-methoxy-2,2-dimethylpyrano[2,3- b]-quinoline (4g), which on hydrolysis with ethanolic hydrochloric acid gave khaplofoline (5). The Prevost reaction of 4-methoxy-3-prenylquinolin-2-one (6) using I2/HgO in acetic acid yielded 4-methoxy-2-isopropylfuro[2,3- b]quinoline (7). Compound 7 on reduction with H2/Pd-C followed by N- methylation and de-O-methylation afforded lunacrine (10a). A similar reaction sequence on 6b gave demethoxylunacrine (10b).
- Sekar,Prasad
-
p. 294 - 296
(2007/10/03)
-
- Quinoline Alkaloids. Synthesis of Khaplofoline, Ribalinine, and Flindersine
-
Reaction of 4-hydroxy-3-prenylquinolin-2(1H)one (5a) with iodine and silver acetate gave a iodopyranoquinoline (6a), which was then converted into the alkaloids khaplofoline (1) and ribalinine (2).Reaction of 5a with iodine and mercuric oxide afforded a mixture of 6a and its angular isomer 7a; the conversion of latter into flindersine (10) is described.Keywords: Pyranoquinoline Alkaloids, Khaplofoline, Ribalinine, Flindersine
- Subramanian, M.,Mohan, P. S.,Shanmugam, P.,Prasad, K. J. Rajendra
-
p. 1016 - 1020
(2007/10/02)
-
- A NEW APPROACH TO HEMITERPENOID TRICYCLIC QUINOLONES. SYNTHESIS OF N-METHYLFLINDERSINE, KHAPLOPHOLINE AND OTHER STRUCTURALLY SIMILAR ALKALOIDS
-
A new and general synthesis of tricyclic quinolone alkaloids is described which, by cyclization of 3-butenyl-4-hydroxyquinolones promoted by mercury(II) ion or by formic acid, affords pyranoquinolones and pyranoquinolones, respectively, with regio- and site-selectivity better than those obtained employing known methodologies. 3-Butenyl-4-hydroxyquinolones have been reacted with mercury(II) acetate to give, after work-up, the corresponding 2-(chloromercurymethyl)pyranoquinolones, which have been reductively demercurated with sodium borohydride and then dehydrogenated by treatment with DDQ.Alternatively, from the same starting compounds the "linear" isomers are obtained by formic acid-promoted cyclization.N-Methylflindersine, khaplofoline and other structurally similar alkaloids have been obtained.
- Bravo, Pierfrancesco,Resnati, Giuseppe,Viani, Fiorenza,Cavicchio, Giancarlo
-
p. 507 - 512
(2007/10/02)
-
- A NEW SYNTHESIS OF ATANINE, KHAPLOFOLINE AND THEIR ANALOGUES
-
Afacile synthesis of Atanine, Khaplofoline and their ananogues is described.The method involves condensation of an appropriately substituted 2-quinolone-3-acetic acid with isobutyraldehyde, as the starting point.
- Ramesh, M.,Arisvaran, V.,Rajendran, S. P.,Shanmugam, P.
-
p. 967 - 970
(2007/10/02)
-
- A NOVEL PHOTOCHEMICAL PRENYLATION REACTION OF HETEROAROMATICS INVOLVING AN ENONE FUNCTION IN THEIR RING SYSTEM
-
In a novel photochemical prenylation of heteroaromatics involving an enone function in their ring system, the key step is an acid-catalyzed C-C bond fission in the head-to-tail adduct formed by photocycloaddition of these heteroaromatics to 2-methyl-3-buten-2-ol to give the heteroaromatics having a 3-methylbut-2-enyl function (or its equivalent) at the α-position of the enone system.Examples using 2-quinolones, 2-pyridones, and coumarins are reported.KEYWORDS---photochemical synthesis; photochemical prenylation; 3,3-dimethylallyalation of heteroaromatics; photochemical 2+2 cycloaddition; 3-(3-methylbut-2-enyl)-2-quinolones; 2-methyl-3-buten-2-ol as prenylation reagent; synthesis of khaplofoline
- Naito, Toshihiko,Momose, Yu,Kaneko, Chikara
-
p. 1531 - 1534
(2007/10/02)
-