*4.3. Peptides*

Recently, two new unique bromopyrrole peptides, seribunamide A (**482**) and haloirciniamide A (**483**), have been extracted from an Indonesian marine sponge of the genus *Ircinia* (Figure 67) [361]. Their relative and absolute stereochemistries were determined by ROESY correlations and on the basis of derivatization [362] with Marfey's reagent, 1-fluoro-2,4- dinitrophenyl-5-L-alanine amide. Compounds **482** and **483** did not show any cytotoxicity against several human tumor cell lines [361].

**Figure 67.** Bromopyrrole peptides **482**–**483** isolated from marine sponges.

In 2015, the structurally unique cyclopeptides hormaomycins B (**484**) and C (**485**) were discovered from a mudflat-derived *Streptomyces* sp. [363] (Figure 68). Both compounds **484** and **485** possess very rare 3-(2-nitrocyclopropyl)alanine units and their absolute configurations were determined by comparing their CD spectra with that of a related hormaomycin. Hormaomycins B (**484**) and C (**485**) showed significant inhibitory effects against various Gram-positive bacteria (MIC values ranging between 0.23 μM and 56 μM), whereas, for Gram-negative bacteria, MIC values between 0.9 μM and 115 μM were determined [363].

**Figure 68.** Macrocyclic peptides **484**–**486** containing a pyrrole motif on their N-termini.

At this point, the cyclopeptidic and highly antitumor active pyrrole alkaloid cyclocinamide A (**486b**) should also be mentioned, which was isolated from a sponge of the genus *Psammocinia* by Crews and co-workers back in 1997 [364]. Roughly twenty years later, a total synthesis of **486b** by the Konopelsky group led to the revision of its absolute stereoconfiguration from **486a** to **486b** (Figure 68) [365].
