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π-Conjugated organoboron molecules, which are easy to prepare, stable against moisture, and easy to functionalize, are scarce. Here, we report a one-pot synthesis of an air-stable organoboron compound, dithienooxadiborepine 1 in 17% yield on a 600 mg scale without separation or handling an air-sensitive intermediate. Dithienooxadiborepine 1 showed excellent stability under ambient conditions, allowing conventional column chromatography purification. Functionalization of 1 was realized via direct bromination using NBS and further Stille coupling reactions, giving access to longer π-conjugated molecules 5A and 5B. Single-crystal structures of compounds 4, 5A, and 5B not only unambiguously verified the chemical identity of dithienooxadiborepine 1 but also revealed that both the seven-member oxadiborepine ring and the 5–7–5 fused dithienooxadiborepine ring system are planar. UV–vis absorption and fluorescence emission measurements of 5A and 5B showed bathochromic shifted absorption and emission relative to 1, evidencing good π-conjugation. Cyclic voltammograms of 5A and 5B displayed two reduction peaks corresponding to two electron-accepting events at two boron atoms. These results proved dithienooxadiborepine 1 a potent π-conjugating building block for electron-accepting materials.

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Background: Berberine (BBR) is a quaternary ammonium alkaloid isolated from the Traditional Chinese Medicine Coptis chinensis. It possesses a plethora of pharmacological activities because its unique structure properties make it readily interact with macromolecules through π-π stacking and electrostatic interaction. Its anti-tumor effects are receiving more and more attention in recent years. Cytotoxicity and anti-proliferation are the important anti-tumor modes of BBR, which have been studied by many research groups. Objectives: This study aims to review the structural modifications of BBR and its cytotoxic derivatives. Also, to study the corresponding structure-activity relationship. BBR showed potential activities toward tumor cells, however, its modest activity and poor physicochemical properties hindered its application in clinical. Structural modification is a common and effective approach to improve BBR's cytotoxic or anti-proliferative activities. Results: The structural modifications of BBR, the cytotoxic or anti-proliferative activities of its derivatives, and the corresponding structure-activity relationship (SAR) were summarized in the review. Conclusion: The concluded SAR of BBR derivatives with their cytotoxic or anti-proliferative activities will provide great prospects for the future anti-tumor drug design with BBR as the lead compound.