Catechol moiety

In the 3-adrenergic blocking drug pyrroxan (48), the catechol moiety is masked in a doxane ring. The synthesis begins by alkylation of phenyl acetonitrile by 2-chloroethanol to produce alcohol Recuction converts this to amino alcohol which... 

Fenoldopam (76) is an antihypertensive renal vasodilator apparently operating through the dopamine system. It is conceptually similar to trepipam. Fenoldopam is superior to dopamine itself because of its oral activity and selectivity for dopamine D-1 receptors (D-2 receptors are as.sociated with emesis). It is synthesized by reduction of 3,4-dimethoxyphenylacetonitrile (70) to dimethoxyphenethylamine (71). Attack of diis last on 4-methoxystyrene oxide (72) leads to the product of attack on the epoxide on the less hindered side (73). Ring closure with strong acid leads to substituted benzazepine 74. O-Dealkylation is accomplished with boron tribromide and the catechol moiety is oxidized to the ortho-quinone 75. Treatment with 9NHC1 results in conjugate (1,6) chloride addition and the formation of fenoldopam (76) [20,21]. 

The reason why synthesis of natural urushiols involves multistep, tedious procedures is that the reactive unsaturated group cannot be directly introduced on the catechol moiety protection and deprotection of the catechol moiety are... 

A variety of ternary complexes containing catecholate moieties are known. For example, in a trimeric Ni11 core the catecholate serves as a bidentate ligand to one Ni11 and also as a bridge between the two podal and the unique axial metal.766... 

The use of HPLC to analyze biogenic amines and their acid metabolites is well documented. HPLC assays for classical biogenic amines such as norepinephrine (NE), epinephrine (E), dopamine (DA), and 5-hydroxytryptamine (5-HT, serotonin) and their acid metabolites are based on several physicochemical properties that include a catechol moiety (aryl 1,2-dihydroxy), basicity, easily oxidized nature, and/or native fluorescence characteristics (Anderson, 1985). Based on these characteristics, various types of detector systems can be employed to assay low concentrations of these analytes in various matrices such as plasma, urine, cerebrospinal fluid (CSE), tissue, and dialysate. 

Some biologically important o-quinones can react with the superoxide ion giving catechol derivatives, which may play a role in many diseases. For example, compounds bearing a nitro-catechol moiety have been claimed to be efficient catechol-0-methyl transferase inhibitors (Suzuki et al. 1992, Perez et al. 1992). The transferase is the first enzyme in the metabolism of catecholamine a hyperactivity of this enzyme leads to Parkinson s disease. Therefore, prediction of biological activity and antioxidant properties of quinones is an important challenge for researchers. 

Incorporation of two catechol moieties into appropriate hexaazacrowns gives the ligands (175) and (176), stability constants of whose Fe complexes are logio.Kli = 37.6 and 36.0, respectively. ... 

Tris-catecholate complexes were prepared from symmetrically and unsymmetrically substituted catechols (LH2) 4-chlorocatechol, 4,5-dichlorocatechol, 4-nitrocatechol, 3,4-dinitrocatechol and 4,5-dinitrocatechol202. All of these complexes are prepared in aqueous solution and are water-stable, down to ca pH 4. The 111 NMR signals for the free and complexed catechol moieties are well separated, and enable the determination of formation constants for each of the complexes, according to equation 46, where L is the catechol dianion. 

The siderophore enterobactin (enterochelin) (64) is a cyclic lactone of three N-(2,3-dihydroxybenzoyl) L-serine moieties produced by E. coli under iron stress. Enterobactin (64) was first isolated from iron-limited cultures of Salmonella typhimur-ium [83], E. coli [84], and Aerobacter aerogenes [84]. Structural analysis has confirmed that 64 chelates iron as a hexadentate ligand via the two hydroxyl groups on each catechol moiety (see Fig. 13) [85]. Of all the siderophores characterized to date, 64 has been shown to have the highest affinity for ferric iron, with a stability constant of 1052 M 1 [86, 87], which is remarkable, considering the affinity of EDTA for iron is 27 orders of magnitude lower. In mammals, serum albumin [88] and siderocalin [89, 90] bind the hydrophobic 64 which impedes siderophore-mediated transfer of iron to bacteria. Consequently, bacteria such as E. coli and... 

The structures of germanium complexes 494a995, 494b"6, 495a"7 and 495b"8 show that the central Ge atom has an octahedral structure with two bidentate deprotonated catechol moieties in equatorial positions. 

Catechol-O-methyltransferase (COMT) is widely distributed throughout the animal and plant kingdom and is primarily associated with the cytosolic fraction of rat liver, skin, kidney, glandular tissue, heart, and brain. In humans, a membrane-bound COMT also has been characterized which is encoded by the same gene as the cytosolic COMT, but with a different transcription start site. Multiple polymorphic forms of COMT may be expressed within a species. COMT catalyzes the transfer of a methyl group from SAM to one of the phenolic groups of a catechol in the presence of Mg2+ ions. With only a few exceptions, all of the methyl acceptor substrates of COMT require the catechol moiety. 

The lipoxygenase family of enzymes catalyse stereospecific oxygenation reactions of fatty-acid substrates. The active site incorporates a non-haem iron centre in as yet an unidentified environment. The active form of the enzyme is the iron(III) state but is converted to iron(II) as the fatty acid is oxidised [91]. Catechol-containing compounds inhibit these enzymes by forming a ternary complex with the iron centre and depending on the substituents on the catechol moiety may even facilitate an internal redox reaction leading to the formation of iron(II) and an inactive form of the enzyme [92,93]. 

The defining structural element found in rolipram and its relatives is the dialkoxyphenyl (catechol) moiety. Although the development of rolipram (then for depression) was terminated early, many companies have since disclosed PDE4 inhibitors intended primarily for indications such as asthma and COPD (chronic obstructive pulmonary disease) [58], For a long time, cilomilast (Ariflo, 54) has appeared to be ahead in this race [59], In November 2003, GSK received an approvable letter from the FDA, despite the FDA advisory panel s earlier negative opinion of the compound. The extent to which new studies may have been requested by the FDA and will delay approval remains to be seen. 

The key glutamine residue (corresponding to Gln817 in PDE5) is involved in an H bonding contact with the catechol moiety. 

Figure 9.17 Fused catechol-type PDE-4 inhibitors where the catechol moiety is part of a bicyclic framework.

The catecholamines (named for the catechol moiety that is part of their structure, Figure 10.1) are important in both the peripheral autonomic system and the central nervous system. Key functions in the periphery are regulation of heart rate and blood pressure. In the brain, they are involved in the regulation of posture and movement, and of psychical functions such as mood and alertness. 

The involvement of metal ions in the color of anthocyanins and flavonoids was discovered almost a century ago, whereby the different colors of flowers originated from the same molecules under different conditions . The crystal structure of the pigment complex affords better understanding of the color and the role of metal ions , where Fe(III) and Mg(II) bind anthocyanins via the catechol moiety and Ca(II) binds flavone glycosides through a vicinal diol on the glycone. 

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