The synthesis and antibacterial activity of pyrazole-fused tricyclic diterpene derivatives.

The diterpenoid compound 5 was identified as an antibacterial lead in our screening of small synthetic natural product-like (NPL) library. A series of novel diterpene derivatives were synthesized and investigated for their activity against Staphylococcus aureus Newman strain and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108 and NRS-271). Among the compounds tested, 42 and 43 showed highest activity with a MIC of 1 μg/mL against strain Newman, 45 and 52 showed the most potent activity with MIC values of 0.71-3.12 μg/mL against five multidrug-resistant S. aureus. All high-antimicrobial active compounds showed no obvious toxicity to human fibroblast (HAF) cells at the MIC concentration.