Synthesis of Biscoumarin and Dihydropyran Derivatives and Evaluation of Their Antibacterial Activity

In an attempt to find a new class antibacterial agents, a series of biscoumarins (1–4) and dihydropyrans (5–13) were successfully prepared. The molecular structures of four representative compounds, that is, 4, 5, 8 and 12 were confirmed by single crystal X-ray diffraction study. These synthesized compounds were screened for their antibacterial activity in vitro against Staphylococcus aureus (S. aureus ATCC 29213), methicillin-resistant S. aureus (MRSA XJ 75302), vancomycin-intermediate S. aureus (Mu50 ATCC 700699), USA 300 (Los Angeles County clone, LAC), Staphylococcus epidermidis (S. epidermidis ATCC 14990), methicillin-resistant S. epidermidis (MRSE XJ 75284) and Escherichia coli (E. coli ATCC 25922). Additionally, there are two classical intramolecular O–H···O hydrogen bonds (HBs) in biscoumarins 1–4 and the corresponding HB energies were further performed with the density functional theory (DFT) [B3LYP/6-31G*] method.