Fragmentation Pathways and Patterns of N-Alkylamides Derivatives

Twenty kinds of N-alkylamides analogues of N-alkylamide esters (A) and N-alkylamides (B) were synthesized by condensation reaction with the N-alkylamides from the root of Anaycclus pyrethrum (L) DC as the lead compounds, HATU as condensation agent, tyramine and faseries of fatty acids as raw material and all of them were new compounds. The results showed that the synthetic route was mild, stable and reliable, and could be used as a way to obtain NAAs derivatives. In order to provide data support for the structure identification of N-alkylamides, mass fragmentation mechanism of 20 N-alkylamides was studied. All the 20 compounds were easy to obtain M+H⁺ at positive ion mode. Class A compounds lost carbonyl alpha at the first, followed by N-position alpha cleavage to form m/z 138.091 2 and m/z 121.063 0, respectively. However, class B compounds were characterized only by N-position alpha cleavage. In vitro tyrosine activation of NAAs derivatives was evaluated by dopa rate oxidation method. The results showed that these compounds had better activity of tyrosinase in vitro, and H-2 was superior to 8-MOP. And it was found that the compounds with phenolic hydroxyl had a greater effect on the activation of mushroom tyrosinase, indicating that phenolic hydroxyl might be the active group for the activation of mushroom tyrosinase. Moreover, from compound H-1 to H-20, the carbon chain increased gradually, and the activation of mushroom tyrosinase decreased gradually, which indicated that the carbon chain length of naas derivatives would affect the activation of mushroom tyrosinase, and the longer the carbon chain, the weaker the activation. The study can provide some references for the structural analysis and application of NAAs.