Terpenoidal Phenazines

Figure 3. Terpenoid phenazines and related derivatives isolated from Streptomyces sp.

A common structural feature of several phenazines from Streptomyces is isoprenylated C- or AAside chains. These terpenoid phenazines were isolated from several different strains besides potentially similar biosynthetic pathways, no obvious pattern in their biological activity could be derived from the literature. 

Phenazines — These are dibenzopyrazine derivatives with fnnctional groups (hydroxy-, carboxy-) at C, and Cg and an oxygen or methyl gronp at Nj and N,o. There are also more complex structures, substituted phenazines, terpenoidal, and carbohydrate-containing phenazines and phenazines derived from saphenic acid. ... 

As the key enzymes of the two electron transport systems with the electron carriers 9 and rac-10 almost exhibit the same specific activity, we may assume that the phenazine system is wholly responsible for the redox process and that the sole function of the terpenoid side chain in 10 is to anchor the electron carrier in the membrane. 

In addition, the idea of the terpenoid side chain of 10 essentially assisting in anchoring the coenzyme in the cytoplasmic membrane without having any impact on the redox potential was to be explored. To this end, a number of phenazine ethers 44a-g were synthesized by Williamson ether synthesis and then investigated by electrochemical methods. And indeed, we were able to identify a good match between the redox potentials of the various phenazine ethers, which turned out to be independent of the side chain structure. 

The same problem occurs with the synthesis of lavanducyanin (65) [85,87] and phenazinomycin (67) [88]. Here, Kitahara et al. used the same approach in that they first generated the phenazine skeleton and performed the AT-allylation as the last step. While the AT-methylation of the unprotected 1-hydroxyphenazine (109) proceeds without any major problems and provides pyocyanin (1) in acceptable yields [89], model experiments already indicate that the allylation of 110 could not be so readily accomplished. As expected, the yields were poor. The only way to bring about the synthesis of 65 is under high-pressure conditions by reaction of 110 with 111, and even so the yield of the natural product remains quite low. Similar problems are encountered with the synthesis of 67 by allylation of 110 with the terpenoid component 112. 

Bacteria overall > 410 Groom, 1992 Scarce diversification between land and sea. ALKAL. indole, phenazine, pyperazine, pyrrole, polypyrrole. PEPT. various classes, including siderophores. POLYKET. lactones, macrolides, quinones. CARBOH. (amino)glycoside, terpenoids hi hi ... 

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