Structure‐activity relationship studies on naphthoquinone analogs. The search for new herbicides based on natural products

Abstract

BACKGROUND Allelopathy and bioassays constitute fundamental tools in the search for new herbicide templates. The work described here is a continuation of a previous study focused on the structure–activity relationships between transport phenomena and phytotoxic activity. Different modifications were made to the naphthoquinone backbone and two key factors were identified as being responsible for changes in activity: lipophilicity and the nature of the functional group. The study of other naturally occurring and semi‐synthetic naphthoquinones was also proposed. RESULTS A total of 12 5‐O‐acyl plumbagins and 18 analogs with unsaturated and aromatic substituents at positions 2 and 5 were synthesized. These compounds were evaluated in the wheat coleoptile bioassay and against Standard Target Species (STS) and three weeds, namely Echinochloa crus‐galli L., Lolium rigidum Gaud. and Lolium perenne L. A strong structure–function relationship was observed for the different naphthoquinones and root and shoot length were the parameters that were most affected. CONCLUSION Strong inhibitory effects were observed for the isomeric forms 23 and 33 and the derivatives with a free hydroxyl group, i.e. 24 and 30, gave values higher than 70% inhibition for root length in barnyardgrass and perennial ryegrass. These results highlight the potential of these compounds as models in the development of herbicides based on natural products. © 2019 Society of Chemical Industry

Synthesis of aminonaphthoquinone derivatives with Ceric Ammonium Nitrate (CAN) as a catalyst: NMR characterization and in silico reaction mechanism

“…Subsequently, the compounds 2-amino-1,4-naphthoquinones, 2-amino-3methyl-1,4-naphthoquinone, and 3-amino-5-hydroxy-1,4-naphthoquinone were synthesized with a molar ratio of 1:1 (starting compound/catalyst). The results obtained from the reaction conditions were compared and discussed respect to those obtained in the absence of catalyst reported by our research group and other authors [2,18].…”

“…Naphthoquinones are aromatic compounds very abundant in nature, distributed in higher plants, bacteria, fungi, arthropods, and individual representatives of the animal kingdom [1][2][3]. Aminonaphthoquinones are of great interest in medicinal chemistry due to the variety of biological activities they present as cytotoxic, antimalarial, antifungal, antibacterial, anti-inflammatory, and antitumor agents [4][5][6][7][8][9][10].…”

“…We have previously reported the synthesis of 2-amino-1,4-naphthoquinone and 2amino-3-methyl-1,4-naphthoquinone by the reaction between hydrazoic acid (formed in situ) and 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone, respectively [2,18]. In this work, it has been studied the effect of the ceric ammonium nitrate (CAN) catalyst in this type of amination reaction.…”

Natural Products in Pest Management: Innovative Approaches for Increasing their Use

“…All speakers produced a paper based on their presentation or a related topic for this special issue of Pest Management Science . Two related papers, one by a participant and the other by non‐participants have been added . This issue provides a broad overview of the present and future status of natural product and biopesticide uses in pest management.…”

“…Two related papers, one by a participant and the other by non-participants have been added. 1,2 This issue provides a broad overview of the present and future status of natural product and biopesticide uses in pest management.…”