Catechol groups

A cyclic borate can be used to protect a catechol group during base-catalyzed alkylation or acylation of an isolated phenol group the borate ester is then readily hydrolyzed by dilute acid. ... 

Cyclic carbonates have been used to a limited extent only (since they are readily hydrolyzed) to protect the catechol group in a polyhydroxy benzene. 

Combining catalytic enantioselective hydroboration (see p. 342) with animation has provided certain amines with good enantioselectivity. In this procedure the catechol group is replaced by methyl prior to the animation step. 

From Pseudomonas mendocina five siderophores were isolated by chromatography. They are reported to have identical molecular masses of 1,152 Da (the also reported 3a) value of 929 Da is an error L. E. Hersman, private communication) and an identical amino acid composition, which has not been revealed 141a). Color reactions show the presence of a hydroxamate, but not of a catecholate grouping. A gene analysis suggests a partial sequence acyl-Asp-Dab-Ser-formylOHOm-Ser-formylOHOm where asparagine could be OHAsp and the C-terminal ornithine cOHOm 9b). In which way the five isomeric siderophores with identical molecular masses differ from each other is not clear. 

The catecholamines are biogenic amines that have a catechol group. Their biosynthesis in the adrenal cortex and CNS starts from tyrosine. 

Additional information As indicated in the reaction above, the catechol group is very readily oxidised upon exposure to light or air. Oxidation results in such compounds turning brown, solutions of isoprenaline and related compounds must contain antioxidants as preservatives. 

Adrenaline is present as a vasoconstrictor in some local anaesthetic injections in a much smaller amount than the local anaesthetic itself, which obscures the absorption of adrenaline in the UV region. The selectivity of UV/visible spectroscopy for the analysis of adrenaline can be increased by complex formation, which occurs between iron (II) and molecules containing a catechol group (Fig. 4.13). These complexes are purple in colour and absorb at ca 540 nm at much longer wavelengths than for instance local anaesthetics, which do not form such complexes. The adrenaline in the injection is quantified against a standard solution of adrenaline. 

Injections of local anaesthetics often contain low concentrations of adrenaline in order to localise the anaesthetic for a time by constricting blood vessels in the vicinity of the injection. Adrenaline can be analysed by straight-phase chromatography, for instance on silica gel, but this generally requires strongly basic conditions under which the catechol group in adrenaline is unstable. Adrenaline is... 

As a result of these condensation processes, concentrations of meth-oxy-containing malvidin anthocyanins decline more quickly in red wines than hydroxycinnamic acids such as caffeic acid with easily oxidizable catechol groups (De Beer et ah, 2008). This is particularly the case when higher levels of SO2 are maintained (Tao et ah, 2007), an observation that can also be linked to the ability of free SO2 to readily regenerate the original caffeic acid form (Makhofkina and Kilmartin, 2009). 

The two possible homologues, with either one or two methyl groups on the methylene carbon of the methylenedioxy group of MDA, are also known. The ethylidene compound (the acetaldehyde addition to the catechol group) has been encoded as EDA, and the acetone (isopropylidine addition to the catechol group) is... 

It had been anticipated by Barger and Dale (13) in their classic (1910) article that adrenaline probably was not the chemical mediator, for this theory involves the assumption of a stricter parallelism between the two actions than actually exists. Adrenine has, in common with other methylamino bases of its catechol group, the property of exaggerating inhibitor as compared with motor effects. The action of some other bases, particularly of the amino and ethylamino bases of the catechol group, corresponds more closely... 

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