Secondary metabolites by chemical screening, 18. Narbosines, new carbohydrate metabolites from Streptomyces

In the culture broth of two new Strepomyces strains several novel 2,3,6‐trideoxy‐L‐threo‐hexose (rhodinose) metabolites, narbosines A to E (2–6, 8, 9), were detected besides α‐N‐acetylanhydro‐L‐ornithine (11) by using the chemical screening method. Their structures were deduced from spectroscopical data as well as from chemical transformations. Narbosine A (2/3) was shown to be a 1:1 anomeric mixture of α‐L‐rhodinopyranosyl‐(1→4) ‐α/β‐L‐rhodinopyranose, the others are partially oxidatively and reductively transformed derivatives of 2/3. A destinct antiviral activity was observed for the described metabolites.