Cyclic Peptides of the Nocardamine Class from a Marine-Derived Bacterium of the Genus Streptomyces

Two new cyclic peptides (2 and 3) along with the previously reported nocardamine (1) were isolated from the culture broth of an actinomycete of the genus Streptomyces isolated from an unidentified marine sponge. On the basis of the results of combined spectral analyses, the structures of the new compounds were defined to be the dehydroxy and desmethylenyl derivatives of nocardamine, respectively. The new compounds exhibited weak inhibition against the enzyme sortase B.