To explore the potential anti-tumour activities of xanthone derivatives, 26 hydroxylxanthones and benzoxanthones and their structurally modified analogues were examined for potential cytotoxic activities against eight human cancer cell lines. Most of the xanthone derivatives exhibited a higher degree of cytotoxicity on HepG2 cells than on the other seven cancer cell lines. Compound 24 (1,3,7-Trihydroxy-12H-benzo[b] xanthen-12-one) showed the highest degree of cytotoxicity of the tested compounds against HepG2 cells and demonstrated good tumour specificity by exhibiting a much higher degree of cytotoxicity against HepG2 cells than against normal liver cells (L02). Several valuable structure-activity relationships were derived from the cytotoxicity data. In addition, we found that compound 24 could downregulate the expression of the Mcl-1 protein, induce changes in the mitochondrial membrane potential and induce apoptosis in HepG2 cells via the mitochondrial pathway. Compound 24 was also shown to inhibit topoisomerase (topo) II activity and downregulate the levels of both topo II mRNA and protein in HepG2 cells. The present results suggest that due to its potent cytotoxicity and good tumour selectivity, compound 24 may be exploited as a potential lead compound in the development of a new anti-tumour agent with specific activity against liver cancer.
Highly enantioselective conjugate cyanation of alkylidenemalonates with KCN was achieved under mild phase-transfer conditions with a bifunctional phase-transfer catalyst. The effect of Brønsted acid additives was examined based on the hypothetical catalytic cycle, and the Brønsted acid additive was found to be essential to promote the conjugate cyanation efficiently.
Telaprevir building block: Efficient asymmetric synthesis of bicyclic amino acid as a core structure of telaprevir has been accomplished via phase‐transfer catalyzed stereoselective conjugate addition of glycine derivative to cyclopent‐1‐enecarbaldehyde. This synthetic method can be applied to the asymmetric synthesis of 3‐substituted prolines.
N-Heterocyclic boryl (NHB) is emerging as an important type of versatile ligand; however, its electronic and steric properties are far from well-known, which is the bottleneck for its rational design. Herein, theoretical evaluation of the scales in electronic and steric properties for various NHBs is presented with NHB−Ir(CO) 3 as the model complex. The calculated Tolman electronic parameters (TEP) reveal general trends about the influence of substitution, backbone saturation, ring size, and heteroatoms. The percent buried volume (%V bur ) of NHBs generally increases with the volume augmentation. The facilitating roles of the PIO-based Bond Index between NHB and the Ir center and the %V bur on TEP were also analyzed. The systematic scales should be essential for the design, application, and mechanistic understanding of the NHB-based complexes or molecules.
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