Beta-lactam compounds containing a protected C-acetyl group, process for their preparation and pharmaceutical compositions containing them

The invention relates to new heterocyclic compounds containing a protected C-acetyl group. More particulary, the invention concerns new compounds of the formula (VI) (VI) wherein R1 is hydrogen or a group suitable for a temporary protection or amides, X is hydroxyl, halogen, cyano or an -O-SO2-R2 group, in which R2 is lower alkyl or aryl, Y1 and Y2 together form a group suitable for a temporary protection of a keto group. The new compounds possess anaphylactic properties and are valuable intermediates of thienamycin synthesis. Their preparation and the new intermediates obtained during their preparation are also within the scope of the invention.