Synthesis and Biological Activity Evaluation of Novel α‑Amino Phosphonate Derivatives Containing a Pyrimidinyl Moiety as Potential Herbicidal Agents

Abstract

To find novel high-activity and low-toxicity herbicide lead compounds with novel herbicidal mode of action, series of novel α-amino phosphonate derivatives containing a pyrimidinyl moiety, <b>I</b>, <b>II</b>, <b>III</b>, and <b>IV</b>, were designed and synthesized by Lewis acid (magnesium perchlorate) catalyzed Mannich-type reaction of aldehydes, amines, and phosphites. Their structures were clearly identified by spectroscopy data (IR, ¹H NMR, ³¹P NMR, EI-MS) and elemental analyses. The bioassay [in vitro, in vivo (GH1 and GH2)] showed that most compounds <b>I</b> exhibited good herbicidal activities; for example, the activities of compounds <b>Ib</b>, <b>Ic</b>, <b>Ig</b>, <b>Ii</b>, <b>Ik</b>, and <b>Im</b> were as good as the positive control herbicides (acetochlor, atrazine, mesotrione, and glyphosate). However, their structural isomers <b>II</b> and <b>III</b> and analogues <b>IV</b> did not display any herbicidal activities in vivo, although some of them possessed selective inhibitory activity against Arabidopsis thaliana in vitro. Interestingly, it was found that compounds <b>IVs</b>, <b>IVt</b>, and <b>IVl</b> showed selective insecticidal activities against Aphis species or Plutella xylostella, respectively. Their preliminary herbicidal mode of action and structure–activity relationships were also studied