Regioselective Aromatic Substitution Reaction Research Articles

Xylochemical Synthesis and Biological Evaluation of Shancigusin C and Bletistrin G.

The biological activities of shancigusin C (1) and bletistrin G (2), natural products isolated from orchids, are reported along with their first total syntheses. The total synthesis of shancigusin C (1) was conducted by employing the Perkin reaction to forge the central stilbene core, whereas the synthesis of bletistrin G (2) was achieved by the Wittig olefination followed by several regioselective aromatic substitution reactions. Both syntheses were completed by applying only renewable starting materials according to the principles of xylochemistry. The cytotoxic properties of shancigusin C (1) and bletistrin G (2) against tumor cells suggest suitability as a starting point for further structural variation.

Photochemical Properties of Red-Emitting Tris(cyclometalated) Iridium(III) Complexes Having Basic and Nitro Groups and Application to pH Sensing and Photoinduced Cell Death.

Cyclometalated iridium(III) complexes, because of their photophysical properties, have the potential for use as luminescent probes for cellular imaging. We previously reported on a pH-activatable iridium complex that contains three N,N-diethylamino groups, namely, fac-Ir(deatpy)3 5, which was synthesized via a regioselective aromatic substitution reaction at the 5'-position with tolylpyridine groups of fac-Ir(tpy)3 2. It was found that 5 shows a considerable enhancement in emission intensity in the pH range from neutral to slightly acidic (pH 6.5-7.4) in aqueous solution and selectively stains lysosome in HeLa-S3 cells, due to the protonation of the diethylamino groups. In addition, 5 functions as a pH-dependent singlet oxygen ((1)O2) generator and induces necrosis-like cell death. However, observing the green emission of 5 is often hampered by autofluorescence emanating from nearby tissues. To overcome this problem, we designed and synthesized a series of new pH-activatable Ir(III) complexes that contain diethylamino, guanidyl, and iminoimidazolidinyl groups on the mpiq ligand of Ir(mpiq)3 7 and the tfpiq ligand of Ir(tfpiq)3 8, which exhibit a red emission, namely, Ir(deampiq)3 13, Ir(gmpiq)3 14, Ir(imzmpiq)3 15, and Ir(imztfpiq)3 16. The emission intensity of these Ir complexes is enhanced substantially by protonation of their basic groups, and they induce the necrosis-like cell death of HeLa-S3 cells by photoirradiation at 465 nm. A strong orange-red emission of Ir(mpiq-NO2)3 9 and Ir(tfpiq-NO2)3 10 is also reported.