Synthesis and antibacterial evaluation of New N-acylhydrazone derivatives from dehydroabietic acid

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.