| abstract |
Processes for the preparation of a penem derivative of formula I <IMAGE> I wherein n=0 or 1; R is a carboxy protecting group or H; R1 is hydrogen, a hydrocarbon group substituted or unsubstituted, or lower alkoxy; and R2 is hydrogen, C1-C5 alkyl, carbamoyl N-substituted by lower alkyl or unsubstituted, or an acyl group; and the pharmaceutically acceptable salts thereof. These processes allow one to prepare stereospecifically only 5R derivatives, and are characterized by R2-introduction at a very late stage in the synthesis, thereby enabling a great number of compounds of formula I to be prepared. Penem derivatives are useful antibacterial agents.n[US4508649A] |