Ring Fission of Substituted Catechols

It is convenient to provide a short introduction to the issues encountered in the degradation of chlorinated substrates that produce chlorocatechols as intermediates. An outline of the ring-fission mechanisms has been given in Chapter 3, Part 1, and Chapter 8, Part 3. Three pathways for fission 

Which of the pathways is followed depends therefore on both the organism and the snbstrate that is being metabolized. 

In snmmary, a range of pathways are available for the degradation of halogenated benzoates  

Dioxygenation with concomitant loss of carboxyl and halogen to prodnce catechols (2-, 2,3-, and 2,5-halogenated benzoates) 

Dioxygenation with decarboxylation bnt withont loss of halogen to prodnce chlorocatechols that may be degraded by several ring-fission pathways (3- and 4-chlorobenzoates) Dioxygenation with loss of only halogen to prodnce a dihydroxybenzoate (2-chlorobenzoate) 

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Ring fission. Ring fission of substituted catechols may take place by three pathways intradiol (ortho), extradiol (meta), or distal (1 6) fission. Although extradiol fission is generally preferred for substituted catechols, the product from extradiol fission of... 

Mechanisms for the ring fission of substituted catechols—An outline of the ring fission mechanisms has been given in Section 6.2.1, and the two pathways are compared in Figure 6.81 which of them is followed depends both on the organism and on the substrate that is being metabolized. 

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