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 dipyninone 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 degrees and 61 degrees by molecular dynamics and found to be 66 degrees and 53 degrees in the crystal. Such torsion angles lead to an interplanar dihedral angle (similar to 93 degrees) between the dipyninone and its adjoining pyrrole that is very close to the dihedral angle (similar to 98 degrees) found in intramolecularly hydrogen bonded bilirubin.
Synthesis and properties of mesobilirubins XIIγ and XIIIγ and their mesobiliverdins
摘要:
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 XII gamma), or the "2 + 2" approach, self-coupling two equivalents of a dipyrrinone (to give XIII gamma). Using the "1 + 2 + 1" approach, mesobilirubin III alpha was also prepared. Mesobilirubins XII gamma and XIII gamma are more polar than mesobilirubin III alpha and unlike III alpha 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 XII gamma isomer exhibiting Cotton effect intensities nearly as strong as those from the III alpha isomer; whereas, the XIII gamma isomer exhibits far weaker intensities. Mesobilirubin III alpha requires glucuronidation for hepatobiliary elimination; whereas, XII gamma and XIII gamma do not, and they are excreted intact across the liver into bile. The corresponding biliverdins XII gamma and XIII gamma are reduced only slowly by biliverdin IX alpha reductase, in contrast to the fast reduction of the natural IX alpha isomer.
An Efficient Method for the Conversion of 2-Bromo-5-tosylpyrroles to the Corresponding 5-Tosylpyrrolinones as the D-Ring of Phycocyanobilin Derivatives
2-Bromo-5-tosylpyrroles were efficiently converted to the corresponding 5-tosylpyrrolinones as the D-ring of phycocyanobilin (PCB) derivatives by treating with DMSO and Zn in TFA in the presence of a catalytic amount of iodine. PCB derivatives modified at the D-ring were prepared in free acid forms employing the resulting 5-tosylpyrrolinones toward structure/function analysis of phytochrome.
在一定量的碘催化下,在反式脂肪酸中用二甲基亚砜和锌处理 2-溴-5-对甲苯磺酰基吡咯烷,可有效地将其转化为相应的 5-对甲苯磺酰基吡咯烷酮,作为植物花青素(PCB)衍生物的 D 环。利用得到的 5-对甲苯磺酰基吡咯烷酮对植物色素进行结构/功能分析。