Synthesis of Δ1-carbapenem derivative by aldol condensation method

The Δ¹-carbapenem derivative($\text{6}$) was prepared by the aldol condensation of the dialdehydic compound($\text{5}$) with piperidinium acetate. Careful hydride reduction followed by benzoylation gave $\text{7}$b, which was successfully decarbalkoxylated to $\text{8}$. The X-ray structure analysis of $\text{8}$ showed the C-3 carboxylate group and C-5 H are $\text{cis}$ each other.