Phenazine-1,6-dicarboxylic acid

The accumulation of phenazine-1,6-dicarboxylic acid (154) by mutants of Pseudomonas phenazinium148 which normally produce hydroxy-phenazine derivatives supports a role for (154) in phenazine biosynthesis. In further studies143 with Ps. phenazinium the sequence of hydroxylative steps leading to the various phenazines has been deduced143 148 to be that illustrated in Scheme 15 the biosynthesis deduced for iodinin (156) is in agreement with earlier conclusions about its formation in cultures of another organism (Brevibacterium iodinum ).146... 

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... 

Phenazine-1,6-dicarboxylic acid (1) is a precursor for microbiological transformation to phenazine-6-carboxylic acid. " - Decarboxylation of phenazine-l,6-dicarboxylic acid (1) in refluxing diphenyl ether affords a mixture of phenazine (2 yield 33%) and phenazine-l-car-boxylic acid (3 yield 25% mp 242-243... 

The above results do not allow one to decide whether one or two molecules of shikimic acid are involved in the biosynthesis of the phenazine nucleus but there is other evidencethat the number of molecules involved is two. If this is accepted there are two ways in which the shikimic acid units can be arranged, (181) and (182) (181) is preferred, for such an arrangement of C-, units is to be seen in phenazine-1,6-dicarboxylic acid (183) and in the griseoluteins, e.g. griseolutein A (184). ... 

Phenazines.— The phenazine ring system is common to some thirty microbial metabolites, " some of which bear carbon substituents at C-1 and C-6, e.g. phenazine-1,6-dicarboxylic acid (167). " This skeletal arrangement suggests a derivation from two molecules of anthranilic acid and this idea is made more... 

This latter observation correlates with the observation that (129) is a precursor for lomofungin (130) in Streptomyces lomodensis. It seems clear from the combined evidence that phenazine-1,6-dicarboxylic acid (129) is a precursor for all microbial phenazines. Failure to observe incorporation of (129) in Pseudomonas, with (by contrast) positive results in actinomycetes, may be attributed to differences in permeability of the cell walls cf. ref. 127). 

Dihydroxyphenazine-l,6-dicarboxylic acid (157) has been isolated as its dimethyl ester from Pseudomonas cepacia Although the acid (157) has been proposed as an intermediate in phenazine biosynthesis before phenazine-1,6-dicarboxylic acid (152), the necessary loss in vivo of two phenolic hydroxy-groups in the formation of (152) or, e.g., (153), makes this highly unlikely, and preliminary testing " of the hypothesis supports this view. The dihydroxy-acid (157) could, however, be an intermediate, and more reasonably so, in the biosynthesis of compounds like lomofungin (155) at a stage after (152). 

Scheme 1. Proposed General Biosynthetic Pathway of Common Phenazine Precursors, Phenazine-1-carboxylic Acid and Phenazine-1,6-dicarboxylic Acid ...

Phenazine natural products are believed to be secondary metabolites derived from a mutual primary metabolite. Most of the investigation of phenazine biosynthetic pathways has been carried out in Pseudomonas strains, but results from studies of Streptomyces support the belief that these species have similar biosynthetic pathways. Accordingly, it has been shown that phenazine-1,6-dicarboxylic acid (Iq) and phenazine-1-carboxylic acid (Ih) are precursors for more complex phenazine metabolites. 

The cleavage of fused pyrazines represents an important method of synthesis of substituted pyrazines, particularly pyrazinecarboxylic acids. Pyrazine-2,3-dicarboxylic acid is usually prepared by the permanganate oxidation of either quinoxalines or phenazines. The pyrazine ring resembles the pyridine ring in its stability rather than the other diazines, pyridazine and pyrimidine. Fused systems such as pteridines may easily be converted under either acidic or basic conditions into pyrazine derivatives (Scheme 75). 

Another novel synthesis of phenazines was introduced by Vagg and co-workers <00JHC151>. The key step was the reaction of dicarboxylic acid 230 with various 1,2-diamines to give 231, 232, and 233. Each was a potential polydentate ligand capable of interacting with DNA via their extended phenanthroline or phenazine components. 

The X-ray crystal structures of pyrazine V.JV -dioxide (134) <02AX(E)1253>, the P-polymorph of phenazine (135) <02AX(C)181>, cobalt(III) complexes of pyrazine-2,6- and pyridine-2,6-dicarboxylic acids <02JIC458>, and bis-urea-substituted phenazines <02ZN(B)937> were reported. Fluorescent pyrido[l,2-a]quinoxalines 136 prepared as pH indicators were examined by X-ray crystallography <02JCS(P2)181>, as were macrocyclic quinoxaline-bridged porphyrinoids obtained from the condensation of dipyrrolylquinoxalines 137 and 1,8-diaminoanthracene... 

Phenazines.—Evidence had been obtained with some micro-organisms, but not with others (Pseudomonas and related organisms), that phenazine-l,6-dicarboxylic acid (121) is the first phenazine to be formed, i.e. the one from which all others derive (cf. Vol. 10, p. 28). The negative results that were obtained with (121) were... 

Batchelor, E., Klinowski, J. and Jones, W. (2000). Crystal engineering using co-crystallisation of phenazine with dicarboxylic acids. J. Mater. Chem. 10,... 

Naphthoquinones condense with benzene-1,2-diamine (25) in a similar manner to yield benzophenazines e.g. 1,2-naphthoquinone 28 undergoes reaction with benzene-1,2-diamine (25) in acetic acid to yield benzo[a]phenazine-l,6-dicarboxylic acid (29). ... 

On treatment with alkaline potassium permanganate phenazine undergoes ring cleavage to give either quinoxaline-2,3-dicarboxylic acid [1, yield 70% mp 190°C (dec.) ] or. under more vigorous reaction conditions, pyrazinetetracarboxylic acid (see Houben-Weyl, Vol. 4/1 b, p 641 and 643). 

Phenazine-l,6-dicarboxylic acid (167) might appear to be the phenazine formed initially by the coupling of two shikimic acid derivatives, but [2,4- H2]-phenazine-l,6-dicarboxylic acid (as 167) was not incorporated into pyocyanin (173) in Ps. aeruginosa, or iodinin (180) in Brevibacterium iodinum Ps. iodina). ... 

Phenazines.—Consideration of structural relationships between the various microbial phenazines, in association with evidence on the way in which these metabolites are formed from two molecules of shikimic acid (151), leads to phenazine-l,6-dicarboxylic acid (152) as a likely common intermediate (Scheme 8), but it has not been found to act as a precursor for various phenazines, exemplified by phenazine-1-carboxylic acid (153). Although the dimethyl ester of (152) has been reported to be a precursor for (153) in Pseudomonas aureo-faciens, it could not be confirmed as such under various conditions. The dihydro-derivative (156) was likewise found not to be a precursor for (153) and (154) in P. aureofaciens. ... 

Consequently, it was considered that iodinin was derived from anthra-nilic acid, or a related intermediate, via phenazine-l,6-dicarboxylic acid. The intermediates for the formation of this alkaloid remain to be clarified. 

Observed limitations include partial decarboxylation during ring closure in the synthesis of phenazine-1,9-dicarboxylic acid as well as poor yield and very low reactivity of ketal-protected ketone diphenylamine in the cyclization step of saphenic acid synthesis. The deprotected ketone was cyclized and reduced in one step, affording the desired saphenic acid in satisfactory yields. 

It has been claimed that dimethyl phenazine-1,6-dicarboxylate (128) is a precursor for 1-carboxyphenazine in Pseudomonas aureofaciens cf. ref. 8. This claim has been disputed careful checking showed that neither (128) nor the corresponding acid (129) was incorporated into phenazines produced by this organism. This has been supported by the results of other workers, who have found that (128) is metabolically inert in P. aureofaciens. Moreover, neither (129) nor (128) was incorporated into phenazines in P. phenazinium. On the other hand, efficient incorporations have been recorded of (129), but not of (128), into iodinin (127) and related phenazines in three actinomycetes, i.e. Streptomyces thioluteus, Microbispora amethystogenes, and M parva ... 

Phenazines compounds based on the phenazine ring system (Table). All known naturally occurring P. are produced only by bacteria, which excrete them into the growth medium. Both six-membered carbon rings of P. are biosynthesized in the shikimate pathway of aromatic biosynthesis, via chorismic acid (not from anthranilate, as reported earlier). The earliest identified biosynthetic intermediate after chorismate is phenazine 1,6-dicarboxylate, which has been isolated from Pseudomonas phenazinium and from non-... 

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