Coumarins, Chromones, and Chromanones

Several 2,2,8-trimethylchromenes (115-118) have been isolated from Pteris longipinna 91). 

3-Carboxyesculetin (123) (94) and 4-isopropyl-6-methylcoumarins (124, 125) 86) have been isolated from ferns. However, the biosynthetic pathways leading to these compounds are not known. 

Leptorumol (126) is the only chromone so far isolated from ferns (98). 

2-Methyl- (129) and 2-ethyl-5,7-dimethoxychromanone (130) have been isolated from Arachniodes standishii (29). 

Generally speaking, xanthones including C-glycosylxanthones are of little taxonomic value because they seem to occur randomly. 

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