Photodimerization of heteroaryl chalcones: comparative antimicrobial activities of chalcones and their photoproducts

Abstract

The heterocyclic analogues of chalcones were synthesized by Claisen Schmidt reaction of (a) benzaldehyde with 2-acetylfurane, 2-acetylpyrrole and 2-acetylthiophene and (b) acetophenone with furfural, thiophene-2-carbaldehyde and pyrrole-2-carbaldehyde. The photolysis of class (a) and (b) chalcones under UV lamp gave different products. The stereoselective photodimerization of 1-(furane-2-yl)-3-phenylprop-2-en-1-one (1), 3-phenyl-1-(1H-pyrrole-2-yl)-prop-2-en-1-one (2) gave b-truxinic type dimers, (3,4-diphenylcyclobutane-1,2-diyl)bis (furane-2-yl methanone) (7), (3,4-diphenylcyclobutane-1,2-diyl)bis ((1H-pyrrol-2-yl) methanone) (8) by syn head-to-head coupling whereas 3-phenyl-1-(thiophen-2-yl)-prop-2-en-1-one (3) gave d-truxinic type dimers, (3,4-diphenylcyclobutane-1,2-diyl)bis (thiophen-2-yl methanone) (9) by anti head-to-head coupling. The photolytic products of 3-(furane-2-yl)-1-phenylprop-2-en-1-one (4), 1-phenyl-3-(thiophen-2-yl)-prop-2-en-1-one (5) and 1-phenyl-3-(1H-pyrrole-2-yl)-prop-2-en-1-one (6) were identified as corresponding 1,6-di(furane-2-yl)-3,4-diphenylhexa-1,5-diene-3,4-diol (10), 3,4-diphenyl-1,6-di(thiophen-2-yl)hexa-1,5-diene-3,4-diol (11) and 3,4-diphenyl-1,6-di (1H-pyrrol-2-yl)hexa-1,5-diene-3,4-diol (12) pinacol dimers.The antibacterial and antifungal activity of the precursor chalcones and the dimeric products showed antimicrobial activities of different extents with respect to individual compounds. In general, photolysis of heteroaryl chalcones causes the depletion of antimicrobial activity.

Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation

“…The reaction was not sensitive to steric hindrance in the aldehyde, since it tolerates well the presence of ortho substituents (compare the yields in entries 4-5, 7-9 and 15-16). Generally speaking, the substituents at the aromatic ring of the aldehyde component did not have a significant influence in the yield, but it is remarkable that some of the best results corresponded to reactions with methoxybenzaldehyde derivatives (entries 2,11,15,20), in spite of the fact that the electron-releasing nature of the methoxy substituent should lead to a lower reactivity as electrophiles. Since the catalytic affect of the clay can be attributed to the Lewis acid activity of its metallic centers (Scheme 2a), the good reactivity of the methoxy derivatives can be explained by accepting that coordination of the oxygen atom in the OMe group with cationic centers in the clay attenuates its electron-releasing effect (Scheme 2b) [40].…”

“…These properties include antineoplastic [5][6][7], antimalarial [8], antiviral (HIV) [9,10], antibacterial [4,11,12], antioxidant [12] and anti-inflammatory [4,13] activities, among others. These compounds are also flexible scaffolds for the construction of five-and six-membered rings or their subsequent elaboration into polycyclic systems [14,15].…”

Development and Characterization of Synthetic Chalcones-Loaded Eudragit RS 100 Microparticles for Oral Delivery

“…[1][2][3] They exhibit several types of biological activity which varies according to the different substituents in the molecules. Thus, they show good potential for further studies and have attracted considerable interest in recent years.…”

“…Structurally, chalcones, 1,3-diaryl-2-propen-1-ones, consist of open-chain flavonoids in which the two aromatic rings are joined by a 3-carbon α,β-unsaturated carbonyl system. [2][3][4] Recently, Tavares et al 1 developed a series of new 6-quinolinyl N-oxide chalcones as well as the 6-quinolinyl chalcones and N-methyl quinolinium iodide derivatives and evaluated their antifungal and cytotoxic activities. The results showed that the majority of these chalcones demonstrated strong activity against pathogenic fungi and tumor cells.…”

“…Specificity was evaluated through comparison of the representative chromatograms of blank Eudragit ® RS100 microparticles with chalcone methanol solutions (1 and 2). Linearity was determined by calculating the regression line from the peak area ratio and solution concentration (2,4,6,8,16,20,24,30 and 40 µg mL -1 ). Precision was evaluated at two levels: intermediate precision, that is, precision on different days determined by analyzing, in triplicate, three different standard samples (16, 20 and 24 µg mL -1 ) on three different days with a two-day interval between analyses; and system repeatability determined by testing a standard solution (20 µg mL -1 ) 6 times on the same day.…”