4-substituted catechol

FIGURE 3.23 Alternative dioxygenation pathways for 3-substituted catechols (a) extradiol, (b) intradiol, and (c) distal. 

FIGURE 9.2 Ring-cleavage pathways for the biodegradation of 3-substituted catechols. 

Figure 15.7 Production of 3-substituted catechols using a designer biocatalyst.

A major challenge that had to be met arose from the extreme bactericidal properties of phenols and catechols. Most microorganisms are poisoned at phenol or catechol concentrations in the 0.1-1 g/L range. The biocatalyst E. coli JMlOl [pHBP461] is no exception, and was inactivated by 200 mg/L of both 2-phenylphenol and 3-phenylcatechol." ° Furthermore, 3-substituted catechols are of limited stability in aerated aqueous solutions and form multimeric humic-acid-hke stmctures as unwanted side products. 3-Phenylcatechol, for instance, has a half-life time of only 14 h at pH 7.2. 

The condensation of 3-substituted catechols with dimedone under electrochemical oxidation in aqueous medium leads to benzofurans (Equation 120) <2004JOC2637>. 

Table 16.3-6. Preparative-scale production of 3-substituted catechols using E. coli )M101 containing 2-hydroxybiphenyl-3-monooxygenase1141.

A new family of benzo[iilfurans was made by an anodic oxidation of an aqueous solution of 3-substituted catechols, and then coupled with dimedone as depicted below <04JOC2637>. 

Fujiwara, M., L. a. Golovleva, Y. Saeki, M. Nozaki, and O. Hayaishi Extradiol Cleavage of 3-Substituted Catechols by an Intradiol Dioxygenase, Pyrocatechase, from a Pseudomonad. J. Biol. Chem. 250, 4848 (1975). 

This enzyme has the potential for the synthesis of 3-substituted catechols. However, this strain could not be used for the synthesis of catechol. 

Urushiol, the first constituent mentioned, is a mixture of 3-substituted catechol derivatives with a 15 or 17 carbon chain having a olefin number 0-3253,5. The average number of olefins in the side chain of urushiol is 2.0-2.5. Constituents of this Japanese lacquer urushiol are seen to be the same as those of urushiol in poison ivy of U.S.A.5... 

CCD is distinct from 1,2-CTD in its specificity for intradiol vs extradiol cleavage of 3-substituted catechols. Broderick and O Halloran found that less than 0.5% of the 3-methylcatechol product resulted from extradiol cleavage [100]. Bhat et al. observed no... 

Compared with extensive studies on the intradiol oxygenation by model complexes, the extradiol oxygenation has been little studied. The extradiol oxygenation is performed not only by Fe -enzymes but also Fe -enzymes in the case of 3-substituted catechols [119]. Thus, the explanation for the extradiol oxygenation by an Fe complex in Scheme 8 is reasonable. However, the remarkable promotion of extradiol oxygenation by using Fe " " in place of Fe " has indicated that such oxygenation is catalyzed by Fe rather than Fe " ", as in enzymatic systems. The reaction has been explained by Scheme 11 [31]. The Fe " " species may be formed from the Fe species by the side-reaction of oxidation of catechol to quinone. 

A. Schmid, H.-P.E. Kohler, K.-H. Engesser, E. coli 1M109 pHBP461, a recombinant biocatalyst for the regioselective monohydroxylation of ortho-substituted phenols to their corresponding 3-substituted catechols, 1. Mol. Catal. B Enzym. 5 (1-4) (1998) 311-316. 

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