Heteronuclear NOE analysis of bilirubin solution conformation and intramolecular hydrogen bonding

Article abstract of DOI:10.1016/S0040-4020(97)00045-8

¹H{¹H}-Homonuclear and ¹³C{¹H}-heteronuclear NOE (Nuclear Overhauser Effect) experiments carried out on bilirubin analogs (1-5) in CDCl₃ and in CDCl₃-(CD₃)₂SO solutions indicate that the carboxylic acid groups and dipyrrinone lactams and/or pyrroles are linked by intramolecular hydrogen bonding. Nonbonded C-H to H-C and N-H to H-N, and N-H to CO₂H distances were calculated from the NOE data and confirm that the bilirubins adopt a folded, ridge-tile shape in solution.