Plant activators are compounds, such as analogs of the defense hormone salicylic acid (SA), that protect plants from pathogens by activating the plant immune system. Although some plant activators have been widely used in agriculture, the molecular mechanisms of immune induction are largely unknown. Using a newly established high-throughput screening procedure that screens for compounds that specifically potentiate pathogen-activated cell death in Arabidopsis thaliana cultured suspension cells, we identified five compounds that prime the immune response. These compounds enhanced disease resistance against pathogenic Pseudomonas bacteria in Arabidopsis plants. Pretreatments increased the accumulation of endogenous SA, but reduced its metabolite, SA-O-β-d-glucoside. Inducing compounds inhibited two SA glucosyltransferases (SAGTs) in vitro. Double knockout plants that lack both SAGTs consistently exhibited enhanced disease resistance. Our results demonstrate that manipulation of the active free SA pool via SA-inactivating enzymes can be a useful strategy for fortifying plant disease resistance and may identify useful crop protectants.

Isobenzofuran can be prepared from o-phthalaldehyde using hydrosilane. The formed isobenzofuran is trapped by an alkene via a Diels-Alder reaction. Further dehydration proceeds to furnish the conjugated aromatic compound. This multistep reaction was promoted by catalytic amounts of Sc(OTf)(3).

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With the objective of improving the poor water solubility of the potent antitumor compound SN-38, 10-O-substituted SN-38 derivatives were developed by the introduction of fluoroalkyl, fluorobenzoyl, or bromobenzoyl groups. The 10-O-fluoropropyl-substituted compound 2 {(S)-4,11-diethyl-9-(3-fluoropropoxy)-4-hydroxy-1H-pyrano[3',4':6,7]indolizino[1,2-b]quinoline-3,14(4H,12H)-dione} was found to be 17-fold more soluble than SN-38 in phosphate-buffered saline, and it exhibited a level of biological activity ≈50 % that of SN-38 in a cytotoxicity assay using the prostate cancer cell line PC-3. Five other derivatives did not show solubility improvements to the same extent, but their activities in cytotoxicity assays were nearly the same as that of SN-38. In vivo studies of 2 with PC-3 tumor-bearing mice revealed that it has higher antitumor activity than SN-38, even at lower dosage. These results will promote the medicinal chemistry application of 10-O-modifications of SN-38 and help reestablish the potential this drug. Furthermore, the inclusion of fluoro and bromo substituents means that the synthetic strategy developed here may be used to obtain F- or Br-labeled SN-38 derivatives for in vivo positron emission tomography studies.

N,N,N¢,N¢-(tetrakis-2-pyridylmethyl)ethylenediamine (TPEN) derivatives bearing a polymerizable double bond in the substituent structure of the pyridine ring were synthesized and subjected to copolymerization with N-isopropylacrylamide in the presence of azobisisobutyronitrile. The obtained poly(TPEN-NIPA) gels show thermoresponsive swelling/shrinking behaviors, and are used for the extraction of cadmium(II) (Cd II ) ions from an aqueous solution to examine the relationship between gel characteristics and extraction performance. Polymer gels composed of TPEN derivatives bearing C3, C4, C10 and branched C3 spacer chains were synthesized, and the temperature-dependent Cd ion extraction behaviors of the gels were compared. The gels extracted Cd II ions efficiently from the aqueous solution in a swelling state at 5 1C, whereas little extraction was observed at 45 1C in the shrinking state. Poly(TPEN-NIPA) gel with branched C3 spacers (C3b) shows excellent thermoresponsive extraction performance.