Syntheses and biological studies of novel spiropiperazinyl oxazolidinone antibacterial agents using a spirocyclic diene derived acylnitroso Diels−Alder reaction

Several novel oxazolidinone antibiotics with a spiropiperazinyl substituent at the 4′-position of the phenyl ring were synthesized through nitroso Diels-Alder chemistry and the in vitro antibacterial activities were evaluated against various Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, Enterococcus faecalis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and mycobacteria (Mycobacterium vaccae, Mycobacterium tuberculosis). Analogs (8a and 12) were active against selected drug resistant microbes, like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) and had no mammalian toxicity in a Hep-2 cellular assay (CC50 >100 μM).