Structure and thermal interconversion of cyclobilirubin IX alpha.

摘要: One of the two main photoproducts in bilirubin metabolism during phototherapy neonatal hyperbilirubinaemia is (EZ)-cyclobilirubin. However, it has not yet been possible to come a final conclusion as its chemical structure, despite fact that much effort expended on problem. The present paper demonstrates (EZ)-cyclobilirubin formed by intramolecular cyclization C-3-vinyl group with position at C-7 rather than C-6, without delta-lactone-ring formation. evidence comes from 13C-n.m.r. spectra, which indicate an oxygen-bound quaternary carbon atom present, and 1H-n.m.r. orientation methyl C-2 equatorial; these findings are supported mass spectra. existence both epimeric relationship between (EE)- (EZ)-cyclobilirubins A B steric isomers hydrogen methyl-group protons observed paired signal new signals C-7, C-3 beta appear spectra extremely similar that, furthermore, thermal interconversion observed.