Process for carbapenem synthesis

A process for synthesizing a compound represented by formula I:

• or a pharmaceutically acceptable salt thereof, wherein R1 and R2 independently are H, C1-10 alkyl, aryl or heteroaryl, said alkyl, aryl or heteroaryl being substituted or unsubstituted, comprising deprotecting a compound of formula II:
• by hydrogenolysis in the presence of a prereduced metal catalyst belonging to the group consisting of palladium, platinum and rhodium, and a base to give a solution of formula I, extracting a solution containing a compound of formula I or 3.
• or a pharmaceutically acceptable salt thereof, wherein each X+ is a charge-balancing group, and R1 and R2 are as described above with a C4-10 alcohol in the presence of an ion-pairing reagent, while maintaining a pH of the aqueous phase between neutral and mildly basic, and isolating the compound of formula I or 3 from the resulting aqueous phase, wherein the metal catalyst is a salt or metal powder or supported on solid supports selected from the group consisting of alumina, silica, calcium carbonate, barium carbonate, barium sulfate, strontium carbonate, polymers, or carbon, P is a carboxyl protecting group which can removed by hydrogenolysis, P* is H, H2+, or a protecting group which can be removed by hydrogenolysis, wherein when P* is H2+ a negatively charged counterion is present.