Design, Microwave-Assisted Synthesis and Anti-Diabetic Activity of 2,4,6-Trisubstituted 2-Aminopyrimidine Derivatives

Author

A. Jayakumar, Sivaprakash. K, Srikanth. S, Subhashini. D, Sumithra. D, Dr. J. Karthi, Dr. S. Swarnalatha


Abstract

   Pyrimidine-based heterocyclic scaffolds continue to attract strong interest in medicinal chemistry, since even small changes in substitution pattern can dramatically shift biological activity. In this study, four 2,4,6-trisubstituted 2-aminopyrimidine derivatives (coded TSA-1 to TSA-4) were designed with a pyridine-2-yl group at the 4-position and differently substituted aryl rings at the 4-position. They were synthesized via a two-step route: base-catalysed Claisen–Schmidt condensation of 2-acetylpyridine with substituted benzaldehydes to form chalcones, followed by microwave-promoted cyclocondensation with guanidine hydrochloride to give the target pyrimidines. The microwave step, run at 240 W for no more than five minutes, replaced several hours of conventional reflux, delivering products in 70–92% yield with minimal side-product formation. Structures were confirmed through melting point, solubility studies, and spectral analysis (FT-IR and ¹H-NMR), consistent with the proposed pyrimidin-2-amine framework. The four compounds were evaluated for antidiabetic potential using an in vitro α-amylase inhibition assay, benchmarked against a standard inhibitor. Percentage inhibition varied strongly with the 4-aryl substituent. The nitro-substituted analogue TSA-2 showed the highest activity, approaching the standard's potency at higher concentrations, while the fluoro derivative TSA-3 was the weakest inhibitor. Chloro- and meta-nitro analogues showed intermediate activity. These results suggest a clear structure–activity relationship, where strongly electron-withdrawing, para-oriented substituents favour α-amylase inhibition within this pyridinyl-aminopyrimidine series, reinforcing microwave irradiation as a fast, efficient, low-waste synthetic strategy.



Keywords

2-Aminopyrimidine; Chalcone; Microwave-assisted synthesis; Guanidine cyclocondensation; α-Amylase inhibition; Antidiabetic activity; Green chemistry



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References


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