ORGN 318 |
| Bilirubin, a tetracarboxylic acid, is the cytotoxic yellow pigment of jaundice, produced in healthy adults at a about 300 mg/day by catabolism of heme of damaged or senescent red blood cells. Bilirubin exhibits a special tendency to adopt a ridge-tile conformation which is further stabilized by intra-molecular hydrogen bonding. It is apparently in this pre-organized structure that the bilirubin is able to cross several selective physiological barriers: the placenta (which is important in fetal metabolism), the blood-brain barrier (which leads to irreversible neurological damage), the liver and the kidney (which are the normal selective barriers for bilirubin elimination and hence detoxification). The ability to form intra-molecular hydrogen bonds is thus an important determinant of conformation, stabilization as well as the pigment's unusual polarity and solubility properties. Also, the structure and the degree of ionization of bilirubin in vivo are clearly the key determinant of its biochemical properties. Although the two acidic side chains in bilirubin are simple aliphatic carboxyl groups, the accurate determination of their acidity constants (Ka's) in water has proven difficult because of it's insolubility in physiological pH. In order to determine the pKa of the carboxylic acid group we have designed and synthesized novel methoxy bilirubin. The 1H, 13C-NMR, UV-vis spectroscopy and vapor phase osmometry experiment of methoxy bilirubin will be discussed. |
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Heterocycles and Aromatics
8:00 AM-12:00 PM, Tuesday, March 27, 2007 McCormick Place Lakeside -- Room E350, Level 3, Oral
Division of Organic Chemistry |