A Rapid Synthesis of 4-Oxazolidinones: Total Synthesis of Synoxazolidinones A and B**

A five-step total synthesis of the marine natural product synoxazolidinoneA was achieved through a diastereoselective imine acylation/cyclization cascade. Synoxazolidinone B and a series of analogues were also prepared to explore the potential of these 4-oxazolidinone natural products as antimicrobial agents. These studies confirmed the importance of the chlorine substituent for antimicrobial activity and revealed simplified dichloro derivatives that are equally potent against several bacterial strains.