Novel α‐L‐Rhamnopyranosides from a Single Strain of Streptomyces by Supplement‐Induced Biosynthetic Steps

Various acyl and phenyl α-L-rhamnopyranosides were produced by Streptomyces griseoviridis (strain Tu 3634) in the presence of different supplements. Some of the added aromatic compounds underwent structural transformations prior to rhamnosylation (1, 3, 5, 8, 9). Especially remarkable was the formation of an indole (9) when 3,5-diaminobenzoic acid was added. Other precursors were not accepted by the strain, but did induce or enhance the biosynthesis of aromatic carboxylic acids from the shikimate pathway. These acids were then transformed into the acyl α-L-rhamnopyranosides 10−13. This can be seen as a new strategy of pathway engineering. With derivatives 4 and 14−17 we gained further insight into the substrate specificity of the rhamnosyltransferase, in particular concerning the competition for rhamnosylation between a carboxylic acid and a phenol or aliphatic hydroxyl group. All isolated metabolites were detected by chemical screening and characterized by spectroscopic methods. The biosynthetic abilities of the strain result in a remarkable structural diversity within the family of α-L-rhamnopyranosides. The strain exemplifies the one strain/many compounds (OSMAC) approach. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)