https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:41781 (E)‐N′‐((E)‐1‐(4‐chlorophenyl)ethylidene)‐2‐(1‐(4‐chlorophenyl)ethylidene)hydrazine‐1‐carboximidhydrazide displays methicillin‐resistant Staphyoccoccus aureus (MRSA) and vancomycin‐resistant Enterococci (VRE) MICs of 2 μg mL⁻¹. Herein we describe the structure‐activity relationship development of a novel series of guanidine to 2‐aminopyrimidine isosteres that ameliorate the low levels of mammalian cytotoxicity in the lead compound while retaining good antibiotic activity. Removal of the 2‐NH₂ pyrimidine moiety renders these analogues inactive. Introduction of a central 2‐NH₂ triazine moiety saw a 10‐fold activity reduction. Phenyl to cyclohexyl isosteres were inactive. The 4‐BrPh and 4‐CH₃Ph with MIC values of 2 and 4 μg mL⁻¹, against MRSA and VRE respectively, are promising candidates for future development.]]> Thu 01 Sep 2022 12:33:12 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:44889 N′,2-bis((E)-4-chlorobenzylidene)hydrazine-1-carboximidhydrazide) and the introduction of imine alkyl substituents gave good antibiotic activity. Of note was the increased potency of two analogues against vancomycin-resistant Enterococci (VRE), one of which returned a MIC of 0.5 μg mL⁻¹. Five analogues were found to be equipotent or more potent than the lead 1. Introduction of an indole moiety resulted in the most active robenidine analogue against methicillin-resistant S. aureus (MRSA), with a MIC of 1.0 μg mL⁻¹. Imine C=NH isosteres (C=O/C=S) were inactive. Monomeric analogues were 16–64 μg mL⁻¹ active against MRSA and VRE. An analogue that lacks the terminal hydrazide NH moiety showed modest Gram-negative activity at 64 μg mL⁻¹. A 4-tert-butyl analogue was shown to be active against both Gram-positive and -negative strains at 16–64 μg mL⁻¹. In general, additional modifications with aromatic moieties was poorly tolerated, except with concomitant introduction of an imine C-alkyl group. The activity of these analogues against MRSA and VRE ranged from 8 μg mL−1 to inactive (MIC>128 μg mL⁻¹) with the naphthyl and indole analogues. Gram-negative activity was most promising with two compounds at 16 μg mL⁻¹ against E. coli. Against P. aeruginosa, the highest activity observed was with MIC values of 32 μg mL⁻¹ with another two analogues. Combined, these findings support the further development of the (E)-2-benzylidenehydrazine-1-carboximidamide scaffold as a promising scaffold for the development of antibiotics against Gram-positive and Gram-negative strains.]]> Mon 24 Oct 2022 14:46:25 AEDT ]]>