Presented here are the syntheses of bicyclodilactams as precursors of polymeric lactams. A new preparation for the 2,5-diazabicyclo[2.2.2]octa-3,6-dione was developed. The four possible dimers were prepared from the N-protected cis- and trans-5-amino-6-oxopiperidine-2-carboxylates (Apc's). Base treatment of the trans activated ester led to the polymer. Synthesis of the isomeric 2,6-diazabicyclo[2.2.2]octan-3,5-dione was not successful even under conditions in which substituted compounds were found. From the 1H NMR spectral data for the monomers and dimers, we concluded that the H−H coupling constants for the cis- and trans-Apc monomers are consistent with the low-energy pseudo-chair conformations inferred from structures optimized at the B3PW91/6-31G* level of density functional theory. The two-dimensional NMR spectra of the oligomers give no evidence for β-turn formation in DMSO-d 6.