Effect Of Meta-Substituents On The Radical Scavenging Activity Of 6-Chromanol Derivatives

A series of 8-substituted 6-chromanols, namely, the methyl- (4), methoxy- (5), amino- (6), methylamino- (7), dimethylamino- (8), 1-pyrrolidinyl- (9), piperidino- (10), 1-piperazinyl- (11), and morpholino- (12) derivatives, were synthesized and investigated to determine the effect of substitution meta to the phenolic OH group of a 6-chromanol on the radical scavenging activity. 7 and 9 possessed excellent radical scavenging properties. Our data showed that the lone-pair electrons on the nitrogen atom of the substituent at the m-position donated electron density into the conjugated p-orbitals on the 6-chromanoxyl radical by delta-donation through resonance, enhancing the radical scavenging activity.