Di‐ and Trifluorinated 2‐Azidobenzimidazole Derivatives: Synthesis, Photooxygenation, and 19 F NMR Prediction

Fluorine-Substituted Rhenium(I) Metallocycle: A New Class of Potent Anticancer Agent

Fluorine and nonfluorine substituted rhenium(I) metallocycles, fac-[{Re(CO)3}2(μ-SO4)(L1)2] (C1) and fac-[{Re(CO)3}2(μ-SO4)(L2)2] (C2), respectively, were synthesized using Re2(CO)10, sodium bisulfite, fluorobenzimidazolyl/benzimidazolyl-based ditopic nitrogen-donor ligands (L1/L2), and toluene-acetone via coordination-driven one-pot solvothermal approach. The metallocycles were characterized using elemental analysis, ESI-TOF-MS, ATR-IR, NMR, and PXRD methods. The molecular structures of C1·9(DMSO), C1·(toluene)(acetone), and C2·(toluene) were determined using SCXRD analysis. The in vitro cytotoxicity study of C1 and C2 was performed against cervical (HeLa) and skin (B16) cancer cells. Murine fibroblast (L929) and mouse myoblast (C2C12) cells were used as noncarcinogenic model cell lines for biocompatibility determination. The metallocycles exhibited potent anticancer activity against both cancer cell lines, showing greater efficacy than the commonly used cisplatin. Moreover, fluorine-substituted C1 metallocycle exhibited significantly higher anticancer activity than nonfluorinated C2 metallocycle, indicating a fluorine effect. Further, in-depth studies of C1 on HeLa cells showed elevated intracellular ROS generation, disruption of mitochondrial membrane potential, and antiproliferative properties. The in vitro studies also revealed its ability to bind with DNA and induce changes in cellular morphology, thus leading to DNA damage and cancer cell death by apoptosis. Molecular docking studies of the metallocycles with B-DNA macromolecule revealed the binding sites, binding affinity, and type of noncovalent interactions.

Azido and desamino analogs of the marine natural product oroidin

As part of our program on the synthesis and reactivity of the pyrrole-imidazole alkaloids from marine sponges, the synthesis of the 2-azido analog of the key marine natural product oroidin is reported. In addition, desaminooroidin and its alkyne analog were synthesized. Red-Al reduction of a 4-alkynylimidazole intermediate afforded the (E)-alkene, without having to pass via the (Z)-alkene. Coupling of 4,5-dibromopyrrole-2-carboxylic acid with 2-azidoimidazolylprop-2-en-1-amine was best achieved by EDCI-mediated coupling, which was superior to using the corresponding trichloromethylketone. Use of t-BuOK in acetonitrile can be recommended for the coupling of non-azidated alkenyl and alkynylimidazoles. The azido analog of oroidin underwent click cycloadditions to imidazolyltriazoles.

Aza-BODIPY Route to Ageladine A

The marine natural product ageladine A was synthesized by exploiting novel aza-BODIPY-type boron complexes that allowed the regioselective dibromination of the pyrrole unit, as confirmed by quantum chemical calculation (ωB97XD/TApr-cc-pVDZ). The parent tricycle was accessed by Suzuki-Miyaura cross-coupling employing Buchwald's precatalyst. The boron complex of ageladine A exhibited strong fluorescence that was greater than that of the natural product by a factor of ∼30 and that disappeared in the presence of 2-azido groups.