Synthesis and free radical scavenging properties of dihydroxypyranone compounds

2, 3-Dihydro-3, 5-dihydroxyl-6-methyl-4H-pyran-4-one (Ⅴa) and 2, 3-dihydro-3, 5-dihydroxyl-6- ethyl-4H-pyran-4-one (Ⅴb), two types of dihydroxypyranones, were synthesized respectively by a four-step reaction of acetylation, palladium hydrogenation, carbonyl α-acetoxylation and deacetylation using maltol and ethyl maltol as raw materials. The structure of each product was then characterized by 1HNMR, 13CNMR and HRMS followed by optimization of the synthesis process. Furthermore, the two dihydroxypyranones exhibited excellent antioxidant activity demonstrated by free radical scavenging assay. The scavenging rates against diammonium 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) free radical (ABTS+•), 2, 2-di (4-tert-octylphenyl)-1-picrylhydrazyl free radical (DPPH•) and Galvinoxyl free radical (Galvinoxyl•) of Ⅴb were 88.9%, 83.8% and 68.4% respectively, obviously higher in comparison to vitamin E and 2, 6-di-tert-butyl-4-methylphenol. The structure-activity relationship revealed that introduction of hydroxyl groups into the structure of pyranone or enhancement of electron donating ability of side chain substituents contributed to the free radical scavenging capability improvement. © 2022, Editorial Office of FINE CHEMICALS. All right reserved.