ORGN 550 |
| Bilirubin IXα is the lipophilic, water insoluble, yellow pigment of jaundice. It is produced in mammals as the end product of heme metabolism. Bilirubin IXα is composed of two dipyrrinone units conjoined together through a -CH2- group, and each dipyrrinone contains a propionic acid side chain. Each dipyrrinone unit can rotate independently around the -CH2- in order to reach the lowest energy conformation. The most stable conformation is one with six intramolecular hydrogen bonds, from each dipyrrinone to a CO2H, causing the pigment to adopt ridge-tile conformation. Bilirubin analogs with but one dipyrrinone have long played an important role in understanding bilirubin's chemical, metabolic properties and its photobiology. The simplest known, intramolecularly hydrogen-bonded analog of bilirubin is [6]-semirubin, with a pentamethylene chain linking C9 of the dipyrrinone to the carboxylic acid terminus. In order to explore the propensity of dipyrrinone to form the intramolecular hydrogen bonds with a carboxylic acid we have designed and synthesized 2,3-dimethoxy-[6]-semirubin and 2,3,7,8-tetramethoxy-[6]-semirubin. The 1H-NMR, UV-vis spectroscopy and vapor phase osmometry experiment of these semirubins will be discussed. |
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New Reactions and Methodology, Heterocycles and Aromatics, Bioorganic Chemistry
8:00 PM-10:00 PM, Tuesday, 12 September 2006 Moscone Center -- Hall D, Poster
Division of Organic Chemistry |