Convenient Synthesis of Pyrano[3,2‐g]chromene‐6‐ones from Naturally Occurring Visnagin and Evaluation of their Antimicrobial Activity

Abstract

AbstractIt is well known that chromones possess numerous of biological activities. Due to their significant applications, there are increasing for synthesizing of several chromones but few pyranochromene have been synthesized. So, simple and convenient routes for the synthesizing of new pyrano[3,2‐g]chromenone derivatives in high yields were illustrated using visnagin as starting naturally occurring. Ring opening of visnagin afforded 6‐formyl‐7‐hydroxychromone derivative which was subjected to react with variety of active methlyene derivatives to afford pyrano[3,2‐g]chromenone derivatives. Thus, heating of 6‐formylchromone with aroylacetate gave the 3‐(aroyl)‐pyranochromene‐2,6‐dione. The desired pyranochromene‐3‐carboxamide derivatives were obtained when the precursor 6‐formylchromone was condensed with ethyl 3‐oxo‐3‐(arylamino)propanoates. When 6‐formylchromone was condensed with hippuric acid gave oxazolone derivative rather than pyranochromene derivative. Condensation of 6‐formylchromone with cyanothioacetamide led to the formation of thioamide derivative. 2‐Iminopyranochromene derivatives were synthesized through reaction of 6‐formylchromone with diverse cyanoacetamide derivatives. Finally, reaction of 6‐formylchromone with 3‐(dimethylpyrazolyl)‐3‐oxopropanenitrile gave 3‐cyano‐pyranochromenedione rather than pyrazole derivative. Antimicrobial activity of the synthesized pyranochromenone derivatives was evaluated. Nearly all compounds showed weak effects towards B. subtilis and P. vulgaris. All compounds showed no effects towards S. aureus and E. coli. All compounds showed no effects towards all tested fungi except thioamide derivative 6 showed moderate activity.