Keywords: Glycosides / Metabolism / Biosynthesis / Streptomyces / Structural diversityVarious acyl and phenyl α-L-rhamnopyranosides were produced by Streptomyces griseoviridis (strain Tü 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 in-
Chemical screening with extracts of Streptomyces sp. (strain GT 61 150) resulted in the detection, isolation, and structure elucidation of two newacyl a-L-rhamnopyranosides (1 and 2) and three new rhamnosyllactones A, B2 and B2 (3-5). Rhamnosyllactones Bx and B2 were obtained as a 5 : 1 mixture. The structures were confirmed by spectroscopic analysis, especially 2D-NMRtechniques. The rhamnosyltransferase of our strain is able to connect the sugar moiety to heteroaromatic carboxylic acids and enols. The metabolites 1 and 4/5 as well as previously reported acylrhamnosides 6-ll inhibit the enzyme 3a-hydroxysteroiddehydrogenase (3 a-HSD). THE JOURNAL OF ANTIBIOTICS the strain was in 50% glycerol at -20°C. The glycerolcontaining storage mixture (2 ml) was used to inoculate a 300-ml Erlenmeyer flask containing 100ml of medium 2.In the routine screening course the flask was cultivated on a rotary shaker (180rpm) at 28°C for 6 days for the primary (1) were reached after 6 days. After harvesting, the culture broth (20 liters) was filtered, and the culture filtrate was adsorbed on Amberlite XAD-16(3 liters of resin). The resin was washed with 6 liters of deionized water and the metabolites were eluted with 5 liters of a mixture ofMeOH/H2O (4 : 1). The solution was concentrated to an aqueous residue which was then lyophilized to yield 227g of a dark brown crude material. The whole crude material was suspended in deionized water (1.5 liters) and extracted exhaustively with EtOAc(5 liters) at room temperature. The organic layers were dried with anhydrous sodium sulfate (Na2SO4), and were evaporated to yield a brown-red residue (18 g). This
Spirodionic acid (1), a novel microbial metabolite with a spiro[4.5]decene skeleton, the 6-ethyl-2H-pyrone 5, dihydrosarkomycin (6), and other metabolites were isolated from the strain Streptomyces sp. Tü 6077. Structural elucidation was accomplished by NMR spectroscopic and mass-spectrometric studies, and the biosyntheses of compounds 1, 5, and 6 were investigated by feeding experiments with (13)C-labeled precursors. All results indicate a biogenetic sequence with metabolite 5 and sarkomycin (7) as precursors in the formation of spirocyclus 1 through an intermolecular Diels-Alder-type reaction.
The ability of Streptomyces griseoviridis (strain Tü 3634) to glycosylate various carboxylic acids with L‐rhamnose was investigated by feeding mainly heteroaromatic and aromatic carboxylic acids to growing cultures. The special application of the precursor‐directed biosynthesis (PDB) gave rise to a wide variety of acyl α‐L‐rhamnopyranosides as novel metabolites. The experiments resulted in furanyl, pyrrolyl, thienyl, indolyl, and pyridyl derivatives (1−8), the analogues 9−24 were generated by feeding fluoro‐, hydroxy‐ or aminobenzoic acids or cinnamic acids. All results are discussed with respect to the substrate specificity of the corresponding enzyme system.
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