2- Hydroxyphenazine-1 -carboxylic acid

Phenazines — The phenazines are biosynthesized by the shikimic acid pathway, through the intermediate chorismic acid. The process was studied using different strains of Pseudomonas species, the major producers of phenazines. The best-known phenazine, pyocyanine, seems to be produced from the intermediate phenazine-1-carboxylic acid (PCA). Although intensive biochemical studies were done, not all the details and the intermediates of conversion of chorismic acid to PCA are known. In the first step, PCA is N-methylated by a SAM-dependent methyltransferase. The second step is a hydroxylative decarboxylation catalyzed by a flavoprotein monooxygenase dependent on NADH. PCA is also the precursor of phenazine-1-carboxamide and 1-hydroxyphenazine from Pseudomonas species. - - ... 

Rapid and sensitive HPLC methods were developed for the detection of an antimicrobial growth promoter and its main metabolites containing quinoxaline-2-carboxylic acid <2005MI1495>. The major phenazine pigments of Pseudomonas aeruginosa such as 1-hydroxyphenazine and phenazine-l-carboxylic acid <1997JCH(A)(771)99>, and 2-aminophenazine as an impurity in a bactericide <1999MI632>, were also analyzed by HPLC methods. 

Using ether-treated cells of P. aureofaciens, dicarbonyl-14C2 phenazme-l,6-dicarboxylic acid las (121)1 was found to be an efficient and specific precursor for phenazine-1-carboxylic acid (123), and also for 2-hydroxyphenazine-l-carboxylic acid (124). The rate of growth of the organism appeared to be important, because an incorporation was also recorded of the labelled (121) into (123), albeit at a lower level, with cultures that had been grown rapidly. The position of phenazine-1,6-dicarboxylic acid (121) as a universal intermediate in the biosynthesis of phenazines now seems secure. The previously reported failure of dimethyl phenazine-1,6-dicarboxylate (122) to act as a precursor of phenazines cf. Vol. 10, p. 28 Vol. 9, p. 29) has been confirmed with ether-treated cells of P. aureofaciens. Efficient hydrolysis of (125) to (123) did, however, occur.101... 

The photochemistry of ethyl esters of 2-oxo-carboxylic acids has the participation of both singlet and triplet excited states o. Triplet state lifetimes have been measured and the occurrence of Norrish type II splits in these molecules established. Other flash photolysis studies reported deal with the photoinduced tautomerism of 2-hydroxyphenazine °, 3-methylisoxazolo[5,4-b]pyridine °, and the photolysis of 4,4 -biphenylbiazide °. The tautomerism and phototautomerization of 4(3H)-pyridinethione has been examined theoretically by the infra red isolation technique . The effect of pressure on the photoinduced abstraction reaction of azanaphthalenes in mixed crystals of durene has also been studied. Photosolvolysis of arylmethanols also occurs in aqueous solutions of sulphuric acid . 

Hydroxyphenazine-l-carboxylic acid was shown to be present in cultures producing iodinin (178) (by dilution after feeding [6- C]shikimic acid). This strengthens its assigned position as an intermediate in iodinin biosynthesis. 

It was of interest to see whether the betaine (171) would serve as a precursor for 2-hydroxyphenazine-l-carboxylic acid (177) and 2-hydroxyphenazine, which are produced by Ps. aureofaciens along with 1-carboxyphenazine (170). ° 2-Hydroxyphenazine-l-carboxylic acid could, it was thought, arise by opening of the epoxide ring of (172) in an alternative manner to the one which would give pyocyanin. In the event, however, only 1-carboxyphenazine served as a precursor for (177) and 2-hydroxyphenazine the respective levels of incorporation are in accord with the sequence (170)— (177)— 2-hydroxyphenazine. As 1-... 

Hydroxyphenazine-l-carboxylic acid (li) and 2-hy-droxyphenazine (lb) are believed to be derived sequentially from phenazine-1-carboxylic acid (Ih) via known biotransformation reactions, presumably via an arene oxide intermediate (Scheme 3). In Pseudomonas aureofaciens, an NADPH-dependent reductase is responsible for the hydroxylation to form li, whereas the subsequent decarboxylation to give lb occurs spontaneously and nonenzymatically. ... 

Phenazine-1-carboxylic acid, 2-hydroxyphenazine, and 2-hydroxyphenazine-l-carboxylic acid were extracted from Pseudamonas aureofaciens cultures and analyzed on a Cig column (A = 257 nm) using a 25-min 65/35/0.1 ->0/100/0.1 water/acetonitrile/TFA gradient [1001]. Elution of the components is complete in 15 min and the two carboxylic acids are not resolved using this gradient system. Therefore, it seems prudent to change to a shallower gradient or have an initial isocratic hold period prior to a gradient in order to force a separation. 

In 2013, along with the reports of biologically active compounds, derived by targeted syntheses, a multitude of natural products was found to display antibacterial, antifungal, and anticancer activities. Mehnaz and her colleagues isolated and characterized known compounds phenazine-1-carboxylic acid (159), 2-hydroxyphenazine-l-carboxylic acid (160), 2-hydroxyphenazine (161), and 2,8-dihydroxyphenazine (162) from the biocontrol strain Pseudomonas aurantiaca PB-St2 (Figure 7-9) (13JNP135). 

Analogous feeding experiments with Pseudomonas aureofaciens established that (87) but not (88) was utilised in the formation of 2-hydroxyphenazine-l-carboxylic acid (94) and 2-hydroxyphena-zine (95). These results were interpreted as showing that both of these phenazine metabolites (94 and 95) are metabolites of phenazine-1-carboxylic acid (87) and are formed as outlined above. 

Hydroxyphenazine-l-carboxylic acid (0.2% inc. in Et20-treated cells)... 

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