Polycyclic Oxaarenes

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

FIGURE 10.35 Anaerobic degradation of (a) furan-2-carboxylate and (b) furan-3-carboxylate. 

FIGURE 10.36 Transformation products from 2,2-dimethyl-7,8-dimethoxychromene. 

FIGURE 10.38 Biodegradation of xanthone. (From Neilson, A.H. and Allard, A.-S., The Handbook of Environmental Chemistry, Vol. 3J, pp. 1-80, Springer, Heidelberg, 1998. With permission.) 

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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. 

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. 

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