Indole-containing natural products occurring indoles

Isoindoles are not known to occur as natural products again, there is a marked contrast with the indoles. However, the cytochalasins, a group of mold metabolites having a marked effect on cell division, contain a highly substituted isoindoline nucleus (3). Cytochalasins A and B (4 and 5) have been obtained from Helminthosporium dematioideum,1 cytochalasins C and D (6 and 7) from Metarrhizium anisopliae,8 and the cytochalasins 8 and 9 from the fungus Phomopsis paspalli found on an Indian millet.9... 

The first naturally occurring indole N-glycoside has been encountered in neosidomycin, an antibiotic constituent of Streptomyces hygroscopicusf its structure (3) is also unique in that it is the only natural product known so far to contain methyl 4-deoxy-riho-hexopyranuronate as the sugar component. However, the configuration (d or l) of this sugar unit is at present unknown. 

The indole ring system occurs in a vast number of biologically important natural products. Many syntiietic com-poxmds of pharmaceutical interest also contain indole structural motif. Indoles are also valuable building blocks in a number of synfhetic sfrafegies to many natural products and bioactive compoxmds as well as in optoelectronic fimctional materials. This has led to a widespread interest in research on synthetic strategies to access this motif and hence a number of impressive methods have been developed for synthesizing indole moiety. 

Indole is a metabolite of the amino acid tryptophan that occurs naturally in several yeasts and fungi and contributes to their flavor profile. Above a concentration of about 1 ppm, indole imparts an obnoxious aroma and flavor to dehydrated yeast, and to the products in which they are used. Headspace SPME can be used to determine the amount of indole that is present in powdered yeast using a standard addition technique. It is sometimes difficult to obtain a sample that does not contain indole for use as a blank, so the preparation of a standard curve... 

---