Most of the linear oligopyrroles are of natural provenience. It therefore is not too surprising that the history of linear oligopyrroles and bile pigments resembles the historical developments of natural product chemistry in general. Contemplating such a historical aspect, one may distinguish three more or less distinct steps which are correlated to the methodological aspects of natural product chemistry. In the beginning of such a historical record of a given natural product, there will be a more or less long lasting period or even an epoch in which it will gradually be recognized that a system with interesting properties (e.g., a color) exists, and that these properties may be related to a certain component of the system. This first period, which may be termed the “period of empirism”, ends with isolation, purification and characterization of a pure compound which is responsible for the systems property of interest. This period may last from several thousand years to a few months. The second period may be characterized as the “period of constitution”. The new natural product is treated in various ways depending on the methods available at the given historical time to achieve the construction of a constitutional graph (a structural formula) of the molecule in question. In the early days of this century the methods used for this purpose were micro elemental analysis and a series of degradation and derivation reactions usually culminating in the synthesis of the compound, thereby providing unequivocal proof for the constitutional hypothesis. Nowadays a rich palette of spectroscopic tools like mass and nuclear magnetic resonance spectroscopy as well as X-ray crystallography is at hand to solve the constitution problem.
KeywordsGall Bladder Gall Stone Historical Aspect Bile Pigment Natural Product Chemistry
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