S. Grabovskii, Yu. S. Grabovskaia, A. Antipin
2018
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Abstract
Pyrimidine derivatives are known for their ability to stimulate regeneration processes and modulate the immune response. The authors of the present work studied synthesis and antioxidant activity of 1,3-dimethyl-5-nitro-6-ethyluracil, 1,3-dimethyl-5-amino-6-ethylura-cil, and 1,3-dimethyl-5-hydroxy-6-ethyluracil. It is shown that these compounds can be ob-tained with good yield from simple reagents. Styrene substrates are useful in testing of chain-breaking antioxidants and determination of the inhibition rate constant. The antioxidant activity of synthesized derivatives in the model reaction of autoxidation of styrene in-itiated by azobis(isobutyronitrile) (AIBN) in chlorobenzene was studied. This reaction (in-itiated by the thermal decomposition of AIBN at 37°C under air atmosphere) was followed by monitoring the oxygen consumption with a recording gas-absorption apparatus, which uses as detector a differential pressure transducer. The rate of initiation was measured in a preliminary set of experiments from the length of the induction period, using alpha-tocopherol as a reference antioxidant. Antioxidant properties was determined for 5-amino and 5-hydroxy derivatives. The studied uracil derivatives should be classified as inhibitors of medium reactivity 7.4 × 10 4 1/(M×s). The ethyl group in the 6-position of the pyrimidine ring increases the rate constant of the reaction with peroxyl radicals by 1.2 times for 5-hydroxy derivative and decreases the rate constant and the stoichiometric coefficient for 5-amino derivatives by 1.8 times toward corresponding 6-methyl derivatives. 1,3-Dimethyl-5-hydroxy-6-ethyluracil is became more strong inhibitor by the addition of a ethyl group at the 6-position in comparison with 1,3-dimethyl-5-hydroxyuracil and 1,3-dimethyl-5-hyd-roxy-6-methyluracil.