226223-25-2Relevant academic research and scientific papers
An intramolecularly hydrogen bonded dihydrotripyrrinone
Tipton, Adrianne K.,Lightner, David A.
, p. 425 - 440 (1999)
A yellow tripyrrole analog (1) of bilirubin has been synthesized, and its lone propionic acid group is found to engage in conformation determining, intramolecular hydrogen bonding in solution and in the crystal. Molecular modelling and X-ray crystallography reveal an abbreviated ridge-tile or L-shape conformation in which an essentially planar dipyrrinone is hydrogen bonded to the single opposing propionic acid group. In the (arbitrary) (P)-helicity ridge-tile, the torsion angles about C(10) are computed to be 55° and 61° by molecular dynamics and found to be 66° and 53° in the crystal. Such torsion angles lead to an interplanar dihedral angle (～93°) between the dipyrrinone and its adjoining pyrrole that is very close to the dihedral angle (～98°) found in intramolecularly hydrogen bonded bilirubin.
Synthesis and properties of mesobilirubins XIIγ and XIIIγ and their mesobiliverdins
Sabido, Portia Mahal G.,Lightner, David A.
, p. 775 - 789 (2014/05/20)
The title pigments, with propionic acid groups displaced to the lactam end rings, were synthesized for the first time by the "1 + 2 + 1" approach, coupling two equivalents of a monopyrrole to a dipyrrylmethane (to give XIIγ), or the "2 + 2" approach, self-coupling two equivalents of a dipyrrinone (to give XIIIγ). Using the "1 + 2 + 1" approach, mesobilirubin IIIα was also prepared. Mesobilirubins XIIγ and XIIIγ are more polar than mesobilirubin IIIα and unlike IIIα cannot effectively engage the propionic acid groups in intramolecular hydrogen bonding to the dipyrrinone components. The new mesobilirubins give exciton coupled circular dichroism spectra in the presence of human serum albumin or quinine, with the XIIγ isomer exhibiting Cotton effect intensities nearly as strong as those from the IIIα isomer; whereas, the XIIIγ isomer exhibits far weaker intensities. Mesobilirubin IIIα requires glucuronidation for hepatobiliary elimination; whereas, XIIγ and XIIIγ do not, and they are excreted intact across the liver into bile. The corresponding biliverdins XIIγ and XIIIγ are reduced only slowly by biliverdin IXα reductase, in contrast to the fast reduction of the natural IXα isomer. Graphical abstract: [Figure not available: see fulltext.]
