Synthesis and evaluation of 6-hydroxy-7-methoxy-4-chromanone- and chroman-2-carboxamides as antioxidants.

A series of 6-hydroxy-7-methoxy-4-chromanone- (2a-e) and chroman-2-carboxamides (3a-e) were synthesized and their antioxidant activities were evaluated. While compounds 2a-e were less active, compounds 3a-e exhibited more potent inhibition of lipid peroxidation initiated by Fe(2+) and ascorbic acid in rat brain homogenates. Among them, N-arylsubstituted-chroman-2-carboxamides (3d and 3e) exhibited 25-40 times more potent inhibition than trolox (1). The DPPH radical scavenging activity of compound 3d was comparable to that of trolox.