3,7-diazabicyclo[3.3.0]octane-2,6-diones: synthesis, NMR spectra and structures

Parent 3,7-diazabicyclo[3.3.0]octane-2,6-dione 5, the corresponding 1,5-dic arboxylic acid 4 and esters 3 have been synthesised for the first time; NMR spectra of the compounds were analysed, and the structures of 3b and 5 wer e studied by X-ray crystallography; hydrogen bonding generates self-assembl y in the form of heterochiral infinite diagonal zigzag tape in the crystal of 5, while in the crystal structure of 3b the H-bonded layers consist of h omochiral spirals and heterochiral chains.