Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Novel olefinic-centered macroacyclic compounds involving tetrasubstituted 4-hydroxybenzoic acid fragments: Synthesis, structural characterization and comparison of experimental and computational results
Graphical abstract
Introduction
p-Hydroxybenzoic acid alkyl esters, generally called parabens, are commonly used as additives and preservatives in food processing, pharmaceuticals, beverages, and cosmetic products, etc. [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. The reason for their effective usage is that they possess not only antimicrobial agents but they also have excellent properties, such as stability over a wide pH and temperature range and adequate solubility in water. Parabens have been used as antiseptics due to their powerful chemical stability, antibacterial activities, and low-cost [11], [12], [13], [14]. For these reasons, the synthesis of paraben derivatives is currently of great importance to the scientific community.
Parabens must be used in specific concentrations in commercial products as exposure to excess amounts may have detrimental effects on living organisms. According to European Union standards the highest concentration of a single paraben in a cosmetic product is 0.4% (w/w), and the highest total concentration for paraben mixtures must be less than 0.8% (w/w) [15]. Regarding the synthesis of paraben derivatives, the scientific community has made great efforts to improve their properties [16], [17], [18], [19], [20], [21], [22]. Since parabens and their derivatives are commonly used as antimicrobial agents and preservatives in skin care products, cosmetics and processed foods, we decided to synthesize paraben derivatives and to investigate their physical, theoretical and spectroscopic properties.
In recent years, density functional theory (DFT) has become a premise of great importance for many chemists [23]. DFT provides a versatile and useful description concerning all structures. With this theory, the properties of many electron systems such as the excited state of atoms or electrons, the ground electronic state, electron affinity, the reaction coordinate, and the tautomeric forms of organic and inorganic compounds can be determined [24], [25].
In the light of these facts, the purpose of the present study was to synthesize and characterize novel tetra paraben derivatives 6a,b (Scheme S1 is provided as Supplementary Material).
In this study, the synthesis of tetra paraben derivatives is described. The study also provides physical, theoretical, and spectroscopic characterizations and a structural investigation of tetra paraben derivatives.
Section snippets
Materials and methods
The reactions were carried out under an inert atmosphere using standard Schlenk techniques. 1H NMR and 13C NMR spectra of the compounds were recorded in DMSO-d6 and CDCl3 using an Agilent NMR VNMRS spectrometer at 400 MHz and 100 MHz, respectively. TMS was used as an internal standard. IR spectra analysis was performed on a Bruker Optics Alpha FT-IR in ATR. The Mass spectra were measured with a Micromass Quattro LC/ULTIMA LC–MS/MS spectrometer equipped with ethyl alcohol and chloroform as
Results and discussion
In this study, the compounds shown as 6a,b dialkyl 4,4′-(2-(1,3-bis(4-(alkoxy carbonyl)phenoxy)propan-2-ylidene)propane-1,3-diyl)bis(oxy)dibenzoate were synthesized with a route that is shown in Scheme S1. The required ethene-1,1,2,2-tetra-yl-tetra methylene tetra bromide 1 was obtained according to a method given in the literature [26]. Compounds 6a,b were obtained from the reaction with ethene-1,1,2,2-tetra-yl-tetra methylene tetra bromide 1 with methyl-4-hydroxy benzoate or ethyl-4-hydroxy
Conclusions
In this study, novel dialkyl 4,4′-(2-(1,3-bis(4-(ethoxycarbonyl) phenoxy)propan-2-ylidene) propane-1,3-diyl)bis(oxy) dibenzoate were synthesized and characterized. The structures of novel synthesized compounds were confirmed by various spectroscopic techniques. In order to confirm the geometry of compound 6b, a determination of its X-ray structure was carried out. In addition, the electronic structure of compound 6b was determined by the DFT method. For comparison with experimental results, the
Acknowledgements
We thank Dr. Olaf Walter for the X-ray analysis.
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