ChemInform Abstract: A Racemic Bicyclic Acylamidine from a Tripeptide Derivative

The 2,2,8-triisopropyl-4,5,7,8-tetrahydroimidazo[1,2-a]pyrazin-3,6-dione molecule, C15H25N3O2, has a double bond and two partial double bonds in the bicyclic skeleton, with some π-delocalization along C'1—N3—C'2. The conformation parameters of the diisopropyl (Dip) residue reveals that it is in an unusually high energy conformation. The peptide bond between the glycine and valine residues is cis [Cα3—C'3—N1—Cα1 = −7.0 (3)°]. In the crystal, the molecules are held together in the ac plane of the P2/n space group by intermolecular hydrogen bonds formed around a twofold axis by molecules related by symmetry centres.