Novel benzoic acid congeners of bilirubin.
Three regioisomeric bilirubins and biliverdins with propionic acids replaced by benzoic acids were synthesized from the corresponding xanthobilirubic acids by oxidative coupling. The rubins were found to exhibit widely varying polarity, spectroscopic properties, and stereochemistry. The isomer with ortho benzoic acids (1o) was much less polar than either the meta (1m) or para (1p) because 1o (but not 1m and 1p) can adopt a folded conformation with both carboxylic acids intramolecularly hydrogen bonded to the opposing dipyrrinones. The consequences of such conformational differentiation are found in the varying 1H NMR, UV-vis, and circular dichroism spectral properties.
D019817:Benzoic Acid / Q000737:chemistry*; D001663:Bilirubin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D001664:Biliverdine / Q000031:analogs & derivatives; D002264:Carboxylic Acids / Q000737:chemistry; D002942:Circular Dichroism; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D011758:Pyrroles / Q000737:chemistry; D012709:Serum Albumin / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
D002264:Carboxylic Acids; D011758:Pyrroles; D012709:Serum Albumin; C013337:xanthobilirubic acid; D019817:Benzoic Acid; D001664:Biliverdine; D001663:Bilirubin