A short, stereoselective synthesis of (3R,4R)-4-acetoxy-3-[(R)-1'((t-butyldimethylsilyl)oxy)ethyl]-2-azetidin one, key intermediate for the preparation of carbapenem antibiotics.

A short stereoselective synthesis of the acetoxy azetidinone (1), an important precursor of several biologically active beta-lactam antibiotics, has been accomplished in seven steps and 32.8% overall yield from the easily available and inexpensive (R) ethyl 3-hydroxybutanoate.