Novel aminonaphthoquinone mannich bases derived from lawsone and their copper(II) complexes: synthesis, characterization and antibacterial activity

Abstract

Uma série de novas Bases de Mannich (HL1-HL13) derivadas da 2-hidroxi-1,4-naftoquinona (lausona), benzaldeídos substituídos [C 6 = Bu) were determined by single crystal X-ray diffraction studies. All complexes crystallize in centrosymmetric space groups, with a copper atom in the inversion centre. Two L − coordinate through the naphthalen-2-olate oxygen and secondary amine-N atoms, forming sixmembered chelate rings around the copper atom in a trans-N 2 O 2 environment; spectroscopic data confirm that the other complexes exhibit similar molecular arrangement. The antimicrobial activity of all compounds has been tested on seven different strains of bacteria: Bacillus cereus, Bacillus subtilis, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. In general, Mannich bases were more active than complexes, HL11 (R 1 = OH; R 2 =H; R 3 = Me; R 4 = Bn) and HL13 (R 1 = OH; R 2 = H; R 3 = Br; R 4 = Bn) being the most potent inhibitors. The MIC for the most active compound HL11 against S. Coli was 20 µmol L -1 (8 µg mL ) and well below most values reported for other naphthoquinones.

Mannich bases in medicinal chemistry and drug design

“…Thirteen novel phenolic Mannich bases 116 ( Fig. 22) derived from lawsone, benzaldehydes and primary aliphatic amines, together with their corresponding copper(II) complexes, were tested for antibacterial activity against seven types of bacteria [144]. With a few exceptions, Mannich bases 116 were generally more potent than the corresponding complexes, presumably due to the greater solubility of the pro-ligands.…”

Aminomethylnaphthoquinones and HSV-1: in vitro and in silico Evaluations of Potential Antivirals

“…The three 2-aminomethyl-3-hydroxy-1,4-naphthoquinones 1-3 (Figure 1) were synthesized as described elsewhere [11,17]. Their identity was confirmed by 1 H NMR (Varian VNMRS 300 MHz spectrometer) and their purity, by elemental analysis (Perkin-Elmer CHN 2400 micro analyzer at Central Analítica IQ-USP, São Paulo, Brazil) and melting point measurement (Digital Melting Point IA9100, ThermoFischer Scientific, Waltham, MA, USA).…”

t-BuOK mediated oxidative coupling amination of 1,4-naphthoquinone and related 3-indolylnaphthoquinones with amines

“…2-Amino-1,4-napthoquinone has demonstrated that the amino group in the naphthoquinone structure can change the electron-accepting capacity and therefore result in increased biological activities. 7 What's more, this type of compound possesses several interesting biological properties such as antibacterial, 8 antifungal, 9 and anticancer activities. 10 Therefore, much effort has been devoted to developing synthetic methods for the construction of 2-amino-1,4-napthoquinone derivatives.…”