Synthesis of linear hetarenochromones based on 7-hydroxy-6-formyl(acetyl)chromones

Fused chromones are attracting increasing attention as novel therapeutic agents due to their wide distribution in nature, effective bioactivities and low toxicity. 6-Carbonyl-7-hydroxychromones proved to be versatile synthons for the synthesis of linear hetarenochromones by annulation of heterocycle to the chromone core. The present review is focused on the syntheses of furo[3,2-g]chromones, pyrano[3,2-g]chromones and some of their N-containing analogues, namely chromeno[6,7-d]isoxazoles, pyrano[3',2':6,7] chromeno[4,3-b]pyridine-5,11-diones and pyrano[3',2':6,7]chromeno[4,3-c]pyridine-5,11-diones based on the 7-hydroxy-6-formylchromones or 7-hydroxy-6-acetylchromones and shows the current state of research to date. The methods for the synthesis of the starting 7-hydroxy-6-formylchromones and 7-hydroxy-6-acetylchromones have been also mentioned. The biological activity of naturally occurring and modified synthetic linear hetarenochromones has been also represented.