New luminescent organoboron esters based on damnacanthal: one-pot multicomponent synthesis, optical behavior, cytotoxicity, and selectivity studies against MDA-MBA-231 breast cancer cells

Abstract

Two new fluorescent nitro-substituted organoboron esters derived from damnacanthal were synthetized by the condensation reaction via one-pot multicomponent reaction (3-MCRs) in just 20 minutes with quantitative yields. Both organoboron esters were fully characterized by NMR, vibrational absorption analysis, UV-vis absorption, fluorescence spectroscopy, and high-resolution mass spectrometry. The δ¹¹B of the new organoboron esters 4a and 4b evidenced the formation of the N→B coordination bond and the high-resolution mass spectrometry corroborates the presence of a boron atom in their molecular structure. The photophysical properties of CHCl₃ were analyzed by UV-vis and fluorescence spectroscopy revealing that both materials can be classified as semiconductors with a fluorescence quantum yield of around 1%. Furthermore, the nitro-substituted ester 4b demonstrated to be 1.5 times more potent against MDA-MB-231 (IC₅₀ = 13 μM) than damnacanthal 1 (IC₅₀ = 23 μM) with a low selectivity index (1.075). To the best of our knowledge, this is the first report on new nitro-substituted organoboron esters based on damnacanthal as a biological building block and applied against MDA-MBA-231 breast cancer cells.