Catechol functions

Catechol methyl transferases require the catechol function to be present to bind to the Mg ion. In the search for p2-adrenoceptor selectivity to produce potent bron-chodilators with low cardiovascular effects, changing the 3,4-hydroxy grouping of the catechol to 3,5- or 3-hydroxyl, 4-methyl-hydroxy, proved to be important (Figure 7.25). These compounds now have much improved bioavailability and pharmacokinetics due to their resistance to catechol methyl transferases. 

Compared to NE, the metabolism of the false neurotransmitter metaramind (MR), mediated by catechol-O-methyl transferase (COMT) and MAO, is reduced because of the absence of the catechol function and the presence of an a-methyl group, respectively (Fig. 24) [161],... 

These new siderophores are identified by acronyms based upon CAM derived from catecholamide which results from substituting 2,3-dihydroxylbenzoyl or its derivatives (29) on a series of polyamines. The introduction of a carboxylic moiety at C-4 or a sulpho moiety at C-5 in the benzene ring extends the acronym to CAMC (29, R = -COOH, Ri = H) or CAMS (29, R = H, Ri = -S03H). The introduction of these two substituents leads to increased oxidation resistance of the catechol functions as well as increasing the hydrophilicity257. The participation of the hydroxy group at C-3 in chelation was established by preparation of an equivalent salicylamide siderophore227. Around 30 CAM-type siderophores have now been reported. 

Dobutamine is given by intravenous infusion, since it is not effective orally. Solutions of the drug can exhibit a. slight pink color as a result of oxidation of the catechol function. It has a plasma half-life of about 2 minutes. It is metabolized by COF and conjugation but not by MAO. 

COMT hypothesis. According to this hypothesis. St. John s wort increases the levels of catecholamines at the brain synapses by inhibiting their inactivation by oxidative deamination (MAOl) and by catechol functionalization (catechol-0-methyltransferase [COMTl). Recent studies have shown that hypericins possess such activities only at pharmacologically excessive concentrations. If true, these effects at normal doses are small and do nothing to alleviate depression. Other hypotheses suggest hormonal effects or effects on the dopaminergic system. Hyperforin has become a candidate for the major antidepressant constituent of St. John s wort. 

L.G., and Johansson, G. (1981) Catalytic-oxidation of reduced nicotonamide adenine-dinucleotide by graphite electrodes modified with adsorbed aromatics containing catechol functionalities. Analytical Chemistry, 53 (13). 1979-1982. 

In an EXAFS study of a soil contaminated by alkyltetravalent Pb compounds, Pb is found in the divalent state and complexed to salicylate- and catechol-type functional groups of HS (Manceau et al., 1996). The best spectral resemblance to reference compounds is obtained for a mixture of 60% salicylate and 40% catechol functional groups. Varying the proportion of salicylate and catechol forms within 10 to 20% has minor effects on the general shape of the combined EXAFS spectrum (Manceau et al., 1996). 

Figure 26. Speciation of lead in a soil affected by alkyllead compounds used as antiknock additives in gasoline. The soil EXAFS spectrum (solid) is compared to model spectra from a library of lead compounds. This comparison identifies salicylate and catechol functional groups as the predominant complexing chelates for divalent Pb. Adapted from Manceau et al. (1996). Figure continued on facing page.)...

From tyrosine, a series of enzymatic reactions including ring hydroxyla-tion, deciurboxylation, deamination, and D-methylation are responsible for over 20 majof metabolites of neurochemical interest. All of the above metabolites retain at least an electroactive phent nudeus, and most provide enhanced detectability via vanillyl or catechol functional groups. Table III provides cyclic voltammctric data in 90% 0.1 M citrate (pH 4)/10% methanol for a series of these metabolites. Substituent effects are evident. Gener-aUy the catecholamines with their OKlihydroxyphenyl structures are easiest to oxidize, followed by vanillyl dmvatives such as normetanephrine and vanillylmandelic acid. Simple phenols such as tyrosine remain the most difficult to oxidize in this series. 

Siderophores typically contain hydroxamate or catecholate functional groups which are arranged to form an octahedral cavity the exact size of a ferric iron. 

Using a different approach, the group of Jean-Marie Lehn, the third of Pedersen s fellow Nobel Laureates in 1987, prepared chiral derivatives of 18-crown-6 from protected tartaric acid to give crowns with four acid groups. As an alternative strategy, the Voyer group later used the catechol functional group of L-3,4-dihydroxyphenylalanine (l-DOPA) as a way to incorporate a chiral center into a... 

The catecholate functionality of CTC should make it a more effective metal binder than is CTV, although there are few known examples. A discrete trinuclear chelate complex of deprotonated CTC with Pt(II) has been reported. The manganese hydroxide-linked MeLa tetrahedra of the type discussed in Section 4.1.2 link into a complicated 3D coordination polymer through bridging oxides and sandwich-type interactions to additional Cs + cations that occur between (MnOH)6L4 tetrahedra. ... 

Catechol is a unique and versatile adhesive molecule capable of forming reversible physical interactions and irreversible covalent bonds (Figure 10.2). In this section, various catechol chemical interactions are introduced. Additionally, various chemical modifications used to modulate catechol side chain reactivity and in the preparation of catechol-functionalized polymers are reviewed. 

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