Abstract
Herein we report the synthesis of a series of O-alkyl oximes of flavone and 6-hydroxyflavone using a simple experimental protocol under solvent free conditions with yields up to 87%. Cytotoxicity of all compounds was evaluated against MDA-MB-231, PC-3, A-549 and MRC-5 cells. IC50 values for two compounds were determined to be in the range 28.7-47.8 µM against all tested cell lines. Oxime ethers derivatives showed IC50 values between 28.7 and 49.5 µM against MDA-MB-231, while the best activity was obtained for 6-hydroxyflavone with an IC50 of 3.4 µM against this cell line. Compounds containing the substituent hydroxyl at the position six of flavone system displayed the best antiproliferative activity over MDA-MB-231 cells, being necessary this group to improve the sensibility on this type of cells. The antiproliferative activity of 6-hydroxyflavone is drastically diminished when the carbonyl group of flavone is changed by an oxime ether.
Highlights
Oxime ethers are useful and versatile compounds in organic synthesis, they are commonly prepared and relatively stable to moisture; they can be stored under air during long periods.[1]
The reaction with O‐methylhydroxylamine hydrochloride in methanol under microwave for 30 minutes[10] did not give rise to compound 3a; we decided to perform a new attempt using the former conditions, adding pyridine as the base. This procedure allowed us obtaining the desired oxime ether 3a in a 19% according to 1H nuclear magnetic resonance (NMR) spectra of the crude mixture, as a single isomer
The reaction was monitored by gas chromatography‐mass spectrometry (GC‐MS) and the dichloride intermediate was detected after the first step (a), but no evidence of the formation of 3a was observed after the second one (b)
Summary
Oxime ethers are useful and versatile compounds in organic synthesis, they are commonly prepared and relatively stable to moisture; they can be stored under air during long periods.[1] Oxime is a pharmacophore group present in a variety of compounds with diverse biological activities, for instance, some α,β‐unsaturated oximes are known as anticancer,[2] immunosuppressive,[3] and antibacterial[4] agents. The wide range of biological activities of flavones has attracted great interest in the synthesis of derivatives with the objective of developing new therapeutic agents.[5]. Oxime ether derivatives of flavones could display relevant biological activity, there are only a few reports about these kind of compounds, suggesting that these derivatives are not as promptly prepared. The first synthesis of a flavone oxime was reported in 1952 using
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