Influence of 3-{5-[4-(diethylamino)benzylidene]rhodanine}propionic acid on the conformation of 5-(4-chlorobenzylidene)-2-(4-methylpiperazin-1-yl)-3H-imidazol-4(5H)-one

Molecular Insights into an Antibiotic Enhancer Action of New Morpholine-Containing 5-Arylideneimidazolones in the Fight against MDR Bacteria

In the search for an effective strategy to overcome antimicrobial resistance, a series of new morpholine-containing 5-arylideneimidazolones differing within either the amine moiety or at position five of imidazolones was explored as potential antibiotic adjuvants against Gram-positive and Gram-negative bacteria. Compounds (7–23) were tested for oxacillin adjuvant properties in the Methicillin-susceptible S. aureus (MSSA) strain ATCC 25923 and Methicillin-resistant S. aureus MRSA 19449. Compounds 14–16 were tested additionally in combination with various antibiotics. Molecular modelling was performed to assess potential mechanism of action. Microdilution and real-time efflux (RTE) assays were carried out in strains of K. aerogenes to determine the potential of compounds 7–23 to block the multidrug efflux pump AcrAB-TolC. Drug-like properties were determined experimentally. Two compounds (10, 15) containing non-condensed aromatic rings, significantly reduced oxacillin MICs in MRSA 19449, while 15 additionally enhanced the effectiveness of ampicillin. Results of molecular modelling confirmed the interaction with the allosteric site of PBP2a as a probable MDR-reversing mechanism. In RTE, the compounds inhibited AcrAB-TolC even to 90% (19). The 4-phenylbenzylidene derivative (15) demonstrated significant MDR-reversal “dual action” for β-lactam antibiotics in MRSA and inhibited AcrAB-TolC in K. aerogenes. 15 displayed also satisfied solubility and safety towards CYP3A4 in vitro.

Chlorine substituents and linker topology as factors of 5-HT6R activity for novel highly active 1,3,5-triazine derivatives with procognitive properties in vivo

In the light of recent lines of evidence, 5-HT₆R ligands are a promising tool for future treatment of memory impairment. Hence, this study has supplied highly potent 5-HT₆R agents with procognitive effects, which represent an original chemical class of 1,3,5-triazines, different from widely studied sulfone and indole-like 5-HT₆R ligands. The new compounds were rationally designed as modifications of lead, 4-(1-(2-chlorophenoxy)ethyl)-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (1), involving an introduction of: (i) two chlorines at benzene ring and (ii) varied linkers joining the triazine ring to aromatic ethers. Synthesis, in vitro and in vivo biological tests and computer-aided SAR analysis for 19 new compounds were carried out. Most of the new triazines displayed high affinity (K_i < 100 nM) and selectivity towards 5-HT₆R, with respect to 5-HT_2AR, 5-HT₇R and D₂R. The crystallography-supported docking studies, including quantum-polarized ligand docking (QPLD), indicated that chlorine atoms may be involved in different type of halogen bonding, however, the linker properties seem to predominately affect the 5-HT₆R affinity. 4-[1-(2,5-Dichlorophenoxy)propyl]-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (9), which displayed: the highest affinity (K_i = 6 nM), very strong 5-HT₆R antagonistic action (K_B = 27 pM), procognitive effects in vivo in novel object recognition (NOR) test in rats, a very good permeability in PAMPA model and satisfying safety in vitro, was identified as the most potent 1,3,5-triazine agent so far, useful as a new lead for further research.

The conformational analyses of 2-amino-N-[2-(dimethylphenoxy)ethyl]propan-1-ol derivatives in different environments

Four crystal structures of 2-amino-N-(dimethylphenoxyethyl)propan-1-ol derivatives, characterized by X-ray diffraction analysis, are reported. The free base (R,S)-2-amino-N-[2-(2,3-dimethylphenoxy)ethyl]propan-1-ol, C₁₃H₂₁NO₂, 1, crystallizes in the space group P2₁/n, with two independent molecules in the asymmetric unit. The hydrochloride, (S)-N-[2-(2,6-dimethylphenoxy)ethyl]-1-hydroxypropan-2-aminium chloride, C₁₃H₂₂NO₂⁺·Cl^-, 2c, crystallizes in the space group P2₁, with one cation and one chloride anion in the asymmetric unit. The asymmetric unit of two salts of 2-picolinic acid, namely, (R,S)-N-[2-(2,3-dimethylphenoxy)ethyl]-1-hydroxypropan-2-aminium pyridine-2-carboxylate, C₁₃H₂₂NO₂⁺·C₆H₄NO₂^-, 1p, and (R)-N-[2-(2,6-dimethylphenoxy)ethyl]-1-hydroxypropan-2-aminium pyridine-2-carboxylate, C₁₃H₂₂NO₂⁺·C₆H₄NO₂^-, 2p, consists of one cation and one 2-picolinate anion. Salt 1p crystallizes in the triclinic centrosymmetric space group P-1, while salt 2p crystallizes in the space group P4₁2₁2. The conformations of the amine fragments are contrasted and that of 2p is found to have an unusual antiperiplanar arrangement about the ether group. The crystal packing of 1 and 2c is dominated by hydrogen-bonded chains, while the structures of the 2-picolinate salts have hydrogen-bonded rings as the major features. In both salts with 2-picolinic acid, the specific R₁²(5) hydrogen-bonding motif is observed. Structural studies have been enriched by the generation of fingerprint plots derived from Hirshfeld surfaces.

Antibacterial properties of 5-substituted derivatives of rhodanine-3-carboxyalkyl acids. Part II

Two series of rhodanine-3-acetic and rhodanine-3-propionic acids derivatives having benzylidene and cinnamylidene substituents with additional electron donating and withdrawing groups at the C-5 position, were synthesised. The structures of the obtained derivatives were confirmed by spectroscopic methods and their lipophilicity was screened. The crystal structures were determined for selected compounds. The antibacterial activity of the derivatives was depended on the type of carboxyalkyl group in the N-3 position and on the type of the substituent in the C-5 position. The derivatives of rhodanine-3-propionic acid demonstrated the highest activity against Gram-positive bacteria. However, none of tested derivatives showed activity against Gram-negative bacteria and yeast. We believe that the presence of the N,N-diethylamine group in the aromatic system and the number of carbon atoms in the carboxyalkyl group is more significant for the biological activity than the fact that the benzylidene or cinnamylidene substituent was present at the C-5 position.

5-Arylideneimidazolones with Amine at Position 3 as Potential Antibiotic Adjuvants against Multidrug Resistant Bacteria

Searching for new chemosensitizers of bacterial multidrug resistance (MDR), chemical modifications of (Z)-5-(4-chlorobenzylidene)-2-(4-methylpiperazin-1-yl)-3H-imidazol-4(5H)-one (6) were performed. New compounds (7⁻17), with fused aromatic rings at position 5, were designed and synthesized. Crystallographic X-ray analysis proved that the final compounds (7⁻17) were substituted with tertiary amine-propyl moiety at position 3 and primary amine group at 2 due to intramolecular Dimroth rearrangement. New compounds were evaluated on their antibiotic adjuvant properties in either Gram-positive or Gram-negative bacteria. Efflux pump inhibitor (EPI) properties towards the AcrAB-TolC pump in Enterobacter aerogenes (EA289) were investigated in the real-time efflux (RTE) assay. Docking and molecular dynamics were applied to estimate an interaction of compounds 6⁻17 with penicillin binding protein (PBP2a). In vitro ADME-Tox properties were evaluated for compound 9. Most of the tested compounds reduced significantly (4-32-fold) oxacillin MIC in highly resistant MRSA HEMSA 5 strain. The anthracene-morpholine derivative (16) was the most potent (32-fold reduction). The tested compounds displayed significant EPI properties during RTE assay (37⁻97%). The naphthyl-methylpiperazine derivative 9 showed the most potent "dual action" of both oxacillin adjuvant (MRSA) and EPI (E. aerogenes). Molecular modeling results suggested the allosteric mechanism of action of the imidazolones, which improved binding of oxacillin in the PBP2a active site in MRSA.