The total syntheses of chiloscyphone (1) and isochiloscyphone (2) have been achieved. Furthermore, the synthetic intermediate 5 shows biological activity against methicillin-resistant Staphyrococcus aureus, and compounds 5, 17, and 18, display imipenem-type activity. The tricyclic lactone framework, which includes an α,β-unsaturated ketone moiety, might play a crucial role in the anti-MRSA activity