Sulfones are one of the most important classes of agricultural fungicides. To discover new lead compounds with high antibacterial activity, a series of new sulfone derivatives were designed and synthesized by introducing the aroxymethyl moiety into the scaffold of 1,3,4-oxadiazole/thiadiazole sulfones. Antibacterial activities against three phytopathogens (Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, Xanthomonas axonopodis pv. citri.) were assayed in vitro. As compared to the control of commercial fungicides and some reported sulfone fungicides, seven compounds 5I-1–5I-7 exerted remarkably higher activities with EC50 values ranging from 0.45–1.86 μg/mL against X. oryzae and 1.97–20.15 μg/mL against R. solanacearum. Exhilaratingly, 5I-1, 5I-2 and 5I-4 displayed significant in vivo activity against X. oryzae with protective effect of 90.4%, 77.7%, and 81.1% at 200 μg/mL, respectively, much higher than that exhibited by Bismerthiazol (25.6%) and Thiadiazole-copper (32.0%). And the differential phytotoxicity of active derivatives was preliminarily checked. The results demonstrated that derivative of 2-aroxymethyl-1,3,4-oxadiazole/thiadiazole sulfone can serve as potential alternative bactericides for the management of plant bacterial diseases.
The reaction mechanism of the γ-carbon addition of enal to imine under oxidative N-heterocyclic carbene catalysis is studied experimentally. The oxidation, γ-carbon deprotonation, and nucleophilic addition of γ-carbon to imine were found to be facile steps. The results of our study also provide highly enantioselective access to tricyclic sulfonyl amides that exhibit interesting antimicrobial activities against X. oryzae, a bacterium that causes bacterial disease in rice growing.
An efficient synthesis of highly functionalized chiral β-amino ester derivatives containing benzothiophene and benzothiazole moieties is developed by a Mannich-type reaction using a cinchona alkaloid-derived thiourea catalyst. The desired products were obtained in good yields and high enantioselectivities (~86% yield, >99% ee) using to the optimized reaction conditions. The synthesized compounds were characterized by 1 H-NMR, 13 C-NMR, IR, and HREI-MS analyses. The bioassays identified that compound 5dr has excellent antifungal activity, with a 60.53% inhibition rate against F. oxysporum, higher than that of the commercial agricultural fungicide hymexazol, whose inhibition rate was 56.12%.
Oxidative N-Heterocyclic Carbene-Catalyzed -Carbon Addition of Enals to Imines: Mechanistic Studies and Access to Antimicrobial Compounds. -Tricyclic sulfonyl amides are conveniently and highly enantioselectively synthesized via a sequence of oxidation, -carbon deprotonation, and nucleophilic addition of the -carbon to imines. Some of the newly synthesized compounds are found to exhibit promising antimicrobial activity against X.oryzae. -(ZHENG, P.-C.; CHENG, J.; SU, S.; JIN, Z.; WANG, Y.-H.; YANG, S.; JIN, L.-H.; SONG, B.-A.; CHI*, Y. R.; Chem. -Eur. J. 21 (2015) 28, 9984-9987, http://dx.
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