Design and semisynthesis of new herbicide as 1,2,3-triazole derivatives of the natural maslinic acid

Interesting biological activities (anti-inflammatory, anticancer, antiviral, antioxidant, antidiabetic...) have been reported for maslinic acid (MA) and MA-based compounds. In continuation of our previous work on MA, herbicide potential of Tunisian plant extracts and 1,4-triazolyl derivatives of MA, we now wish to report semisynthesis of new MA-based triazole hybrid compounds with herbicide potential. These compounds were synthesized through Cu-catalyzed azide-alkyne cycloaddition (CuAAC) under microwave irradiation conditions between propargylated MA and a series of phthalimide azides. Here, the first partner of CuAAC reaction (propargylated MA) resulted from propargylation of C-28 carboxylic acid group of isolated MA from the well-known Mediterranean plant Olea europaea L. (Oleaceae). So far, phthalimide azide derivatives were achieved by trapping of N-acyliminium ion, in-situ generated under catalytic condition of Bi(OTf)(3), by aromatic nucleophiles. The cycloaddition reaction afforded regiospecifically 1,4-disubstituted triazoles in good yields. The latter hybrid compounds were shown to exhibit a high inhibition potential of seed germination. This constitutes the first step in development of potent herbicides since one of the final semisynthesized structures can serve as a promising lead candidate for further studies.