478288-11-8Relevant academic research and scientific papers
Novel benzoic acid congeners of bilirubin
Boiadjiev, Stefan E.,Lightner, David A.
, p. 7591 - 7604 (2007/10/03)
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.
Atropisomerism in linear tetrapyrroles
Boiadjiev, Stefan E,Lightner, David A
, p. 7411 - 7421 (2007/10/03)
Novel bilirubin and biliverdin congeners with propionic acids replaced by o-carboxyphenyl exhibit diastereomerism due to axial chirality about the carbon-carbon single bond linking the o-carboxyphenyl group to a pyrrole ring. Evidence for atropisomerism was found even in the monopyrrole precursor, ethyl 3,5-dimethyl-4-(o-carboxyphenyl)pyrrole-2-carboxylate. Like bilirubin, o-carboxyphenyl rubin 1a adopts an intramolecularly hydrogen-bonded ridge-tile conformation in nonpolar solvents. In solutions containing optically active amines or human serum albumin 1a exhibits intense bisignate exciton coupling-type induced circular dichroism for its long wavelength absorption near 400nm.
