Regioselective Epimerisation of cis-3-Amino-4-oxo-azetidine-2-sulphonic acid and Synthesis of Monocyclic β-Lactams

A novel procedure for the regioselective epimerisation of cis-3-amino-4-oxo-azetidine-2-sulphonic acid (3-AAA) into the trans-isomer is described. It was found that a complete inversion of C-3 configuration of the cis-3-AAA takes place during the formation of a Schiff base. The cleavage of the imine bond of the Schiff base in methanol resulted in the generation of trans-3-AAA in good yield. Here is also described a preparation of novel cis- and trans-monobactams with an amidosulphonic acid group on azetidinone nitrogen.