Pyrroles Including Tetrapyrroles

Chemical synthesis of PBG, based on the formation of pyrroles, includes more than 10 steps and gives the product with a yield of 25%. In chemical synthesis from ALA, the yield of PBG is about 10%. Microbiological methods using ALA as a substrate have a good perspective, since the product yield can reach up to 54%. Propionibacteria present a special interest for PBG production, since they have a high natural capacity for the synthesis of tetrapyrrole compounds, for which PBG is a common precursor. 

Structural variations of tetrapyrrolic porphycene 38 (Scheme 17) in such a way that an 18jt-electron conjugation pathway is retained, have furnished a variety of neutral as well as charged porphycene analogues. These variations mainly include replacement of a pyrrole heterocycle with furan, thiophene, or imidazole. 

A major metabolic fate of glycine is the biosynthesis of tetrapyrroles, compounds which contain four linked pyrrole rings. Four classes of these compounds include 1) Heme (an iron porphyrin) 2) Chlorophylls 3) Phycobilins (photosynthetic pigments of algae and 4) Cobalamins (Vitamin B12 and derivatives). 

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