Phenazine alkaloids

In this chapter, the alkaloids of higher plant origin and the alkaloids obtained from microorganisms, such as the pseudan derivatives, as well as pyocyanine and related compounds that possess the phenazine skeleton, are discussed. 

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. 

Phenazinomycin is charaaerized by a phenazine chromophore with a sesquiterpene moiety. The chromophore (N-demethylpyocyanine) of this alkaloid corresponds to that of a pyocyanine derivative and is thought to be derived from anthranihc acid or a related compound, as in the case of pyocyanine. 

Tryptophan (7.25) serves as a precursor for a number of microbial metabolites. A notable example is the ergot alkaloids (Section 7.5.1). Other aromatic amino acids are involved in the biosynthesis of various metabolites. Their origins are through shikimic acid 7,78) (see Section 5.1). Shikimic acid itself, or a close metabolic relative, serves as a source for some metabolites, e.g. phenazines (Section 7.5.5) and the ansamycins (Section 7.6.1). For compounds like the latter, acetate and propionate are also important starting materials for biosynthesis. Another important part source for many metabolites is mevalonate, invariably as a C5 (dimethylallyl) unit. 

Phenazines are not a particularly common structural skeleton for alkaloids, as evidenced by the fact that during the interval from 2007 through April 2014 when this review was completed, there is only a single report of alkaloids of this class that utilized NMR data in any form. 

Solphenazines A-F—Glycosylated Phenazine Alkaloids from Streptomyces sp. Strain DL-93... 

During a survey of actinobacteria known to suppress the growth of Streptomyces scabies, the causative agent of potato scab disease, a series of six new phenazine alkaloids were isolated and characterized by Salomon and coworkers [95]. NMR analysis of the ethyl acetate and butanol extracts of the culture supernatant and mycelium suggested a suite of aromatic compounds that were ultimately determined to be glycosylated 1,6-disubstituted phenazines (107—112). The structure of the phenazine and the various substituents that were substituted at the 1- and 6-positions are shown below. The structures of these phenazines, with the exception of 111, are the first examples of diglycosylated phenazine alkaloids. 

---