In recent years, naturally occurring tetrahydro-β-carboline (THC) alkaloids and their derivatives have been of biological interest. However, few studies and developments have reported the use of such structures in managing plant bacterial diseases. Herein, an array of novel THC derivatives containing an attractive 1,3-diaminopropan-2-ol pattern were prepared to evaluate the antiphytopathogen activity in vitro and in vivo and explore innovative antibacterial frameworks. Notably, target compounds exhibited excellent activities against three rebellious phytopathogens, namely, Pseudomonas syringae pv. actinidiae (Psa), Xanthomonas axonopodis pv. citri, and Xanthomonas oryzae pv. oryzae, at related optimal EC 50 values of 2.39 (II 9 ), 2.06 (I 23 ), and 1.69 (II 9 ) μg/mL, respectively. These effects were superior to those of the parent structure 1,2,3,4-THC and positive controls. In vivo assays showed that II 9 exhibited excellent control efficiencies of 51.89 and 65.45% at 200 μg/mL against rice bacterial blight and kiwifruit bacterial canker, respectively, and I 23 substantially relieved the citrus canker on the leaves. Antibacterial mechanisms indicated that these THC compounds could induce the increment of reactive oxygen species and subsequently endow the tested bacteria with distinct apoptotic behavior. In addition, II 9 could alleviate the hypersensitive response and pathogenicity of Psa. Overall, these simple THC derivatives can be further developed as versatile antibacterial agents.

Abstract. Pseudomonas (P.) aeruginosa is an ubiquitous and metabolically versatile opportunistic pathogen and may cause various life-threatening diseases. Due to increasing emergence of resistance to carbapenems, novel drugs with improved antibacterial activities compared with those of traditional antibiotics are required. In the present study, berberine (BEB), a natural isoquinoline alkaloid, was used in combination with imipenem (IMP), a commonly-used carbapenem, to investigate their antibacterial activities against a clinical P. aeruginosa isolate PA012 and the potential mechanism. Screening revealed that the minimum inhibitory concentrations (MICs) of BEB and IMP were 512 and 256 µg/ml, respectively. The combination of BEB (1/4 MIC) and IMP (1/8 MIC) exhibited a synergistic effect with a fractional inhibitory concentration index of 0.375. The synergism of BEB and IMP was also demonstrated in a time-kill test and by scanning electron microscopic observation. Treatment with BEB at ¼ MIC in combination with IMP at 1/16, 1/8, 1/4 and ½ MIC revealed a concentration-dependent promoting effect of IMP on the intracellular accumulation of BEB and inhibition of bacterial adhesion. Further analysis of gene expression revealed that BEB (1/4 MIC) combined with IMP (1/8 MIC) decreased MexZ, MexX, MexY and outer membrane protein (Opr)M by 38, 35, 46 and 49% in PA012. In conclusion, these results suggested that IMP had synergistic effects with BEB against the clinical isolate PA012 via inhibition of the MexXY-OprM efflux pump.

Ferrocene-derived dicarbaldehydes bearing pro-chiral planes are desymmetrized under the catalysis of chiral Nheterocyclic carbene organic catalysts. The reaction features selective activation and reaction of one of the aldehyde moieties of the ferrocene derivative while leaving the other aldehyde unit untouched. Our reaction affords enantiomerically enriched planar chiral ferrocene products obtained that are amenable for further transformations. Preliminary application studies show encouraging results when our products are explored for catalysis in chemical synthesis and for antimicrobial utilities in pesticide development.

The development of catalyst-controlled methods for direct functionalization of two distinct CÀ H bonds represents an appealing approach for CÀ C formations in synthetic chemistry. Herein, we describe an organocatalytic approach for straightforward acylation of C(sp 3 )À H bonds employing readily available aldehyde as "acyl source" involving dehydrogenative coupling of aldehydes with ether, amine, or benzylic C(sp 3 )À H bonds. The developed method affords a broad range of ketones under mild conditions. Mechanistically, simple ortho-cyanoiodobenzene is essential in the oxidative radical N-heterocyclic carbene catalysis to give a ketyl radical and C(sp 3 ) radical through a rarely explored intermolecular hydrogen atom transfer pathway, rendering the acylative CÀ C formations in high efficiency under a metal-and light-free catalytic conditions. Moreover, the prepared products show promising antibacterial activities that shall encourage further investigations on novel agrochemical development.

The development of catalyst-controlled methods for direct functionalization of two distinct CÀ H bonds represents an appealing approach for CÀ C formations in synthetic chemistry. Herein, we describe an organocatalytic approach for straightforward acylation of C(sp 3 )À H bonds employing readily available aldehyde as "acyl source" involving dehydrogenative coupling of aldehydes with ether, amine, or benzylic C(sp 3 )À H bonds. The developed method affords a broad range of ketones under mild conditions. Mechanistically, simple ortho-cyanoiodobenzene is essential in the oxidative radical N-heterocyclic carbene catalysis to give a ketyl radical and C(sp 3 ) radical through a rarely explored intermolecular hydrogen atom transfer pathway, rendering the acylative CÀ C formations in high efficiency under a metal-and light-free catalytic conditions. Moreover, the prepared products show promising antibacterial activities that shall encourage further investigations on novel agrochemical development.