Atomic oxygen (O(3P)) or ground state oxygen is classified as a reactive oxygen species (ROS). It is a unique diradical because of its high reactivity and selectivity compared to other ROS species. O(3P) can be generated from heterocyclic sulfoxides on UV exposure. This photochemical reaction involves a unimolecular cleavage of the sulfoxide bond to yield the corresponding sulfide and O(3P). When O(3P) is present in biological systems, it may cause oxidative stress leading to cell death or apoptosis. DBTO has been a well-studied O(3P) precursor that cleanly generates the oxidant. However, DBTO is not an ideal candidate for cellular studies due to its poor water solubility. It is also desirable to synthesize precursors that have red shifted absorbance. An increase in benzannulation of DBTO derivatives allows for red shifted absorbance. Previous studies on benzonaptho[2,1,d]thiophene S-oxide (BNTO) has shown that this pre-cursor is able to generate O(3P) in similar yields compared to DBTO on UV-A irradiation at higher wavelengths. Electrophilic aromatic substitution by a halogen in these heterocyclic compounds increase the possibilities of coupling reactions; this synthetic strategy can be used to further improve on chemical and physical properties of O(3P) pre-cursors, making them more compatible for biological studies. In this study, electrophilic aromatic substitution was applied to BNTO to synthesize Br-BNTO through a monobromination reaction. Cell studies were conducted using Br-BNTO on MDA-MB-231 breast cancer cells. Results from the cell studies showed that Br-BNTO was able to significantly decrease the viability of these cells when exposed to UV-A light. The quantum yield for Br-BNTO was experimentally determined to be 0.0044±0.0018. An octene test as a common intermediate test was also performed to determine if Br-BNTO generates O(3P).

Synthesis of 5-bromo-benzonaphtho[2,1,d]thiophene S-oxide and its ability to cause oxidative stress in cells

2019 Spring National Meeting

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