Tetrapeptides possessing a unique skeleton, JBIR-34 and JBIR-35, isolated from a sponge-derived actinomycete, Streptomyces sp. Sp080513GE-23.

Two new modified indole-containing peptides, JBIR-34 (1) and JBIR-35 (2), were isolated from the fermentation broth of a sponge-derived actinomycete identified by phylogenetic methods as a Streptomyces sp. (strain Sp080513GE-23). The planar structures of 1 and 2 were assigned on the basis of 1D and 2D NMR spectroscopy and MS analyses. Further, the absolute configurations of the amino acid residues were determined using Marfey's method.