Synthesis and Antibacterial Evaluation of New N-acylhydrazone Derivatives from Dehydroabietic Acid

Abstract

A series of new N-acylhydrazone derivatives were synthesized in good yields through the reactions of dehydroabietic acid hydrazide with a variety of substituted arylaldehydes. The structures of the synthesized compounds were confirmed by IR, 1H- and 13C-NMR, ESI-MS, elemental analysis and single crystal X-ray diffraction. From the crystal structure of compound 4l, the C=N double bonds of these N-acylhydrazones showed (E)-configuration, while the NMR data of compounds 4a–q indicated the existence of two rotamers for each compound in solution. The target compounds were evaluated for their antibacterial activities against four microbial strains. The result suggested that several compounds exhibited pronounced antibacterial activities. Particularly, compound 4p exhibited good antibacterial activity against Staphylococcus aureus and Bacillus subtilis comparable to positive control. The possible antibacterial metabolism and the strategy for further optimization of this compound were also discussed.

Anti‐Tuberculosis Evaluation and Conformational Study of N‐Acylhydrazones Containing the Thiophene Nucleus

“…. NMR spectral and theoretical studies have previously indicated that acylhydrazones generally exist mainly or solely as mixtures of E NC / E C(O)NH and E NC / Z C(O)NH conformers . The absence, or very low proportions, of Z CN geometric isomers is a consequence of steric hindrance .…”

Mild, Stereoselective, and Highly Efficient Synthesis of N‐Acylhydrazones Mediated by CeCl3·7H2O in a Broad Range of Solvents

“…Under these conditions, the reactions lead to mixtures of ( E ) and ( Z ) diastereomers, with the predominant formation of the ( E ) isomer. Indeed, accurate reports of this method corroborate this observation 14a–14d. The formation of the ( Z ) isomer is directly related to the heat needed for the condensation to occur between the hydrazide and the carbonyl compound, and the E / Z ratio is dependent on the structural features of the starting molecules, as our group has previously demonstrated by 1 H NMR analysis of two hydrazone series that were obtained by heating the reactants in tetrahydrofuran (THF) without an acid catalyst 15.…”

Crystal structures of threeortho-substitutedN-acylhydrazone derivatives

“…N-Acylhydrazones can exist as Z/E geometrical isomers about the C N bond of the hydrazone moiety (Palla et al, 1986). Crystal-structure studies of N-acylhydrazones revealed that the molecules display an E conformation in the solid state (Purandara et al, 2015a(Purandara et al, ,b,c, 2017Gu et al 2012), whereas NMR spectroscopic studies showed the duplicate signals for amide and methylene protons, indicating the presence of two isomers in solution (Lacerda et al, 2012;Lopes et al, 2013). As the stereochemistry of the hydrazone is determined by the various substituents in the hydrazone moiety, we thought it would be interesting to synthesize several ortho-substituted N-acylhydrazone derivatives to explore their effects on crystalstructure parameters and hydrogen-bonding interactions.…”