Oxaarenes

Naturally occurring oxaarenes based on polycyclic pyrans encompass a plethora of structures including the plant polyphenols such as anthocyanins and a-tocopherol (vitamin E). Halogenated dibenzo-p-dioxins and dibenzofurans are formed both as by-products during the manufacture of chlorophenols, and from the incineration of organic matter in the presence of inorganic halides. 

The aerobic degradation of furan-2-carboxylate has already been summarized in Part 1 of this chapter and emphasis is placed here on anaerobic pathways. 

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Although pyridines and quinolines were first produced during the carbonization of coal, they are now available by synthesis in quantities that far exceed those by the former. Phosphorylated ribosides of hydroxylated and aminated pyrimidines and purines make up the basic structure of ribonucleic and deoxyribonucleic acids. The polycyclic oxaarenes are plant metabolites, while thiaarenes are primarily important components of high-sulfur petroleum that must be removed. 

Monooxygenation mediated by the cytochrome P450 system of Streptomyces has been observed in oxaarenes ... 

Three reactions of flavanones may be used to represent the broad classes of biotransformation reactions which have been observed in oxaarenes dehydrogenation, hydroxylation, and ring scission (Figure 6.57) (Ibrahim and Abul-Hajj 1990). 

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