One-step microwave-assisted oxidative removal of 3-methyl and 3-sugar side chain in 2(1H)-quinoxalinone system by selenium dioxide and sodium periodate respectively resulting 2(1H)-quinoxalinone has been reported. Similarly xanthopterin (as acetyl derivative 11) was isolated from selenium dioxide oxidation of 7-methylxanthopterin. In the absence of adjacent lactam moiety, sodium periodate efficiently oxidizes 2-acetylaminopterin tetrols 7 and 8 to 2-acetylamino-6-formylpterin (16) and the quinoxaline tetrols 9 and 10 respectively to quinoxaline aldehyde 17. However, all the compounds remained unchanged on refluxing with selenium dioxide. The new quinoxalone compounds 15 and 18 were simply synthesized by manganese dioxide oxidation of the completely unprotected 3-substituted sugar of 2(1 H)-quinoxalinone 5 and quinoxaline 10 respectively under microwave condition.