Synthesis,in vitro antibacterial and antifungal evaluation of novel 1,3,4-oxadiazole thioether derivatives bearing the 6-fluoroquinazolinylpiperidinyl moiety

A series of structurally novel 1,3,4-oxadiazole thioether derivatives(6a-6z) containing a 6-fluoroquinazolinylpiperidinyl moiety were designed and synthesized using pharmacophore hybrid approach,and their structures were fully characterized by ^1H NMR,^(13)C NMR and HRMS spectra.Among them,the structure of compound 6 d was further corroborated via single-crystal X-ray diffraction analysis.In vitro antibacterial bioassays showed that compounds 6 a,6 g,6 u and 6 v possessed EC_(50) values of 30.4,30.6,27.5 and 26.0 μg/mL against phytopathogenic bacterium Xanthomonas oryzae pv.oryzae,respectively,which were significantly superior to that of commercially-available bactericide Bismerthiazol(85.1 μg/mL).Moreover,in vitro antifungal bioassays indicated that seven compounds demonstrated broad-spectrum fungicidal acitivties against six types of phytopathogenic fungi at 50 μg/mL.The present work showed the potential of 1,3,4-oxadiazole thioether derivatives carrying a 6-fluoroquinazolinylpiperidinyl moiety as effective antimicrobial agents for crop protection,deserving further investigations in the future.

Synthesis and bioactivities of novel 2-(thioether/sulfone)-5-pyrazolyl-1,3,4-oxadiazole derivatives

By introducing the pyrazole moiety into the 5-position of 1,3,4-oxadiazole,a series of novel 2-（thioether/sulfone）-5-pyrazolyl-l,3,4-oxadiazole derivatives were synthesized.Preliminary bioassays suggested that target compounds exhibited appreciable activity against pathogenic bacteria Xanthomonas oryzae pv.oryzae（Xoo） and five phytopathogenic fungi in vitro.Among them,the half-maximal effective concentration（EC_（50）） values of 6c,7a,7b and 7c against Xoo were within 16.6 μg/mL and 65.7 μg/mL,which were better than those of commercial agricultural antibacterial bismerthiazol（92.6 μg/mL） and thiodiazole copper（121.8 μg/mL）.While compounds 7a,7b,and 7c exerted comprehensive antifungal activity toward five plant fungi,which were comparable with that of hymexazol.The results demonstrated that this kind of compounds can be further studied and developed as promising antifungal and antibacterial agents.

Synthesis,Crystal Structure and Antifungal Activity of New Furan-1,3,4-oxadiazole Carboxamide Derivatives

A series of novel furan-1,3,4-oxadiazole carboxamide derivatives (5a~5e) were designed,synthesized and characterized by spectroscopic methods including HR-MS,^(1)H-and ^(13)C-NMR.The crystal structure of compound 5a was determined by single-crystal X-ray diffraction.The compound crystallizes in the triclinic system,space group P■ with a=4.7261(5),b=10.4672(11),c=14.5886(13)?,α=106.081(4)°,β=91.043(3)°,γ=99.456(4)°,Z=2,V=682.48(12)?^(3),M_(r)=348.16,D_(c)=1.694 Mg/m^(3),S=1.008,m=3.025 mm^(-1),F(000)=348,the final R=0.0775 and w R=0.2080 for 2774 observed reflections (I (29) 2σ(I)).There are two kinds of hydrogen bonds (N(3)–H(3A)×××N(2) and C(8)–H(8A)×××O(3)) present in its crystal structure.The preliminary antifungal assay showed that compounds 5b and 5c exhibited significant antifungal activities against several plant pathogenic fungi.

Antiviral and Antibacterial Activities of N-（4-Substituted phenyl） Acetamide Derivatives Bearing 1,3,4-Oxadiazole Moiety

In this paper, a series of N-（4-substituted phenyl） acetamide derivatives bearing 1,3,4-oxadiazole moiety were synthesised. Preliminary bioassays revealed that these compounds not only exhibited favourable antiviral activities toward tobacco mosaic virus （TMV） but also demonstrated sustained inhibition activities against plant pathogenic bacteria, including Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas axonopodis pv. cit- ri. Among the derivatives, TC8 and TC20 exerted the strongest curative activities against TMV, with half-maximal effective concentration （EC50） values of 239.5 and 236.2μg/mL, respectively, which were comparable to that of ningnanmycin （EC50=273.2μg/mL）. Given their simple synthesis, the target compounds can serve as alternative antiviral candidates.