Synthesis and metal ion binding activity of methyl 12-amino-13-nitro-7-oxo dehydrodeisopropylabietate derivatives

Abstract

Starting from dehydrobaietic acid with the analogous structure of carnosic acid, the intermediate methyl 12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate was synthesized through methylation, bromination, carbonylation, and nitration. Subsequently, the coupling of methyl 12-bromo-13-nitro-7-oxo dehydrodeisopropylabietate with aliphatic or aromatic primary amine by Ullmann condensation reaction produced a series of methyl 12-imino-13-nitro-7-oxo dehydrodeisopropylabietate derivatives. In order to probe their antioxidant effects through metal ion chelation mechanism, the metal ion binding abilities on Cu2+ and Fe2+ of these compounds were studied using fluorescence quenching method. The results indicated that each compound showed obvious chelation activity with the binding constants (K A) of the 102 L mol−1 order of magnitude, which implied its potential pharmacology application as antioxidant by the inhibition of Feton reaction through chelation with Cu2+ and Fe2+.