Synthesis and Biological Activities of New Chiral Imidazolinone Derivatives

Abstract

New optically active 2-thio-4-imidazolinones 3 with a chiral carbon at position-3 were synthesized from isothiocyanates 2, which were obtained from aza-Wittig reactions of vinyliminophosphoranes 1 with CS₂, with easily accessible chiral (S)- or (R)-amino acid methyl ester hydrochlorides. 2-Methylthio-4H-imidazolin-4-ones 4 were obtained by the S-alkylation of compounds 3 in the presence of K₂CO₃ causing partial racemization of the enantiomeric pure products. These compounds were identified by MS, IR, ¹H NMR, ¹³C NMR spectroscopy, and elemental analysis. The structures of enantiomers 3c and 3d were also confirmed by X-ray diffraction analysis. The results of preliminary bioassay indicated that compounds 4 exhibited growth inhibition of barnyard grass and cole root and stalk, and fungicidal activities against Fusarium oxysporium, Rhizoctonia solani, Gibberella zeae, Dothiorella gregaria, and Colletotrichum gossypii.

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Keywords:

• Aza-Wittig reaction
• chiral agrochemicals
• crystal structure
• fungicidal activities
• herbicidal activities
• imidazolinone derivatives

Acknowledgments

The authors are thankful for the financial support from National Key Technology R&D Program (Grant No. 2007BAI34B00), the National Natural Science Foundation of China (Grant No. 20876147), and the Opening Foundation of Zhejiang Provincial Top-Key Pharmaceutical Discipline (Grant No. 20050603, 20050610, and 20080602).