Cyclopeptides biosynthesis

The aromatic p-amino acid Adda 74 [114] is a substructure of several cyclopeptides from cyanobacteria, i.e. the microcystins 86 and nodularin 85. More than 60 microcystin and nodularin homologs have already been isolated from the genera Microcystis, Anabama, and Oscillatoria (microcystins) as well as Nodularia (nodularins). A multitude of literature is available on the biosynthesis and biological activity of these hepatotoxins, which can constitute a serious health hazard in fresh water [135]. 

This mechanism also holds for the biosynthesis of the tyrocidins and many additional cyclopeptides, depsipeptides and for the gramicidins A, B and C, as well. 

As the biosynthesis of cyclic peptide antibiotica proceeds independently of the normal RNA-controlled peptide synthesis, one may presume that their elaboration takes place by way of an enlargement of cyclopeptides by insertion of L-amino acids, starting with piperazine-diones. 

In this review, we discuss the isolation, structure, physicochemical and spectral data of all bromotyrosine derivatives isolated from marine organisms. The biosynthesis, total synthesis, and bioactivity of the bromotyrosine derivatives are also reviewed. Neither tyrosine derivatives without halogenation, nor indole alkaloids (with or without halogenation), are included in this review. Proteins or peptides containing bromotyrosine units are not included in this review since they are considered as primary metabolites. Cyclopeptides containing halogenated tyrosine units are, however, discussed in this review. 

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