An Intramolecularly Hydrogen Bonded Dihydrotripyrrinone

摘要

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 55dge and 61deg by molecular dynamics and found to be 66deg and 53deg in the crystal. Such torsion angles lead to an interplanar dihedral angle(approx 93deg) between the dipyrrinone and its adjoining pyrrole that is very close to the dihedral angle(approx 98deg) found in intramolecularly hydrogen bonded bilirubin.