Abstract :The synthetic process of important penem and carbapenem antibiotics intermediate 4-AA was studied. Intermediate (A) in 74.5% yield was prepared by diazotization and nucleophilic substitution reaction of L-thronine with sodium nitrite, hydrochloride acid and sodium hydroxide at -5℃. Intermediate (A) reacted with Intermediate (B) (p-methoxylphenylaminoethyl acetate) for 5 h t o give intermediate(C) in 84.3% yield. Then intermediate (D) in 72.1% yield was synthesized by cyclization reaction of intermediate(C) in the presence of hexamethyldisilazane and lithium amide. Finally, 4-AA was prepared by Hydroxyl protection agent, Hydrolysis, decarboxylation oxidation reaction and deprotection agent with ozone. The tolal yield is 34.5％, HPLC purity is 99.34%.