Pyridines natural occurrence

Unlike their benzene counterparts, thienopyridines do not occur widely in nature. The basic components of a shale oil of high sulfur content were found to contain certain methylthieno[2,3-6]- and -[3,2-6]-pyridines, but no other natural occurrence of the compounds has been reported. 

The commercial availability of basic pyridine derivatives has encouraged a tremendous amount of research into pharmaceutically active compounds. Two reviews in particular list a large number of medicinal compounds (B-80MI20900,77CZ389) based on the pyridine ring. Likewise, the occurrence of benzopyridine natural products with chemotherapeutic activity has stimulated the production of synthetic materials from aromatic amine precursors. Some important examples are presented below. 

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