Halogenated cyclic peptides

Halogenated cyclic peptides Jaspis sp. and Theomlla sp. Jaspamide (10), and theonellamide [59]... 

Several relatively large cyclic peptides have been found to contain halogen. Islanditoxin (91) which was isolated in 1955 from a culture of... 

Peptides may he detected best using the methods found suitable in PC. The popidar ninhydrin reaction is not always sufficiently sensitive with higher peptides it fails utterly with cyclic peptides unless these contain free amino groups in side chains. More generally available and more sensitive (limit of detection about 0.1 (xg) is the N-halogenation of Reindel and Hoppe [73], modified as follows [8, 149] ... 

Didemnum Phenylethylamlne derivatives pyridoacridines alkaloids of pyrrole (lamellarins), Indole (eudistomins), carbazole and guanidine aromatic and heteroaromatic S/N derivatives (thiazole-rich cyclic peptides) halogenated nucleosides... 

The cyclic peptides are ubiqxiitous in the order lithistida, where many structural variations are observed, in particular the existence of bicyclic peptides and also mono- and bicyclic glycopeptides. Several of these complex molecules contain original or atypical a- and P-amino acids, many of them have a a-ketoamide structural element and some have halogen (bromotryptophan) or stilfur atoms (thia-zole). They are all biologically active and most are cytotoxic or have antitumoral or antifungal activity. To provide as complete an overview as possible, the main peptides are presented in Table 19.28. 

Aplysia 260 Terpenes and halogenated terpenes, halogenated cyclic ethers, peptides and cyclic depsipeptides, macrolactones, alkaloids... 

The selective halogenation of glycine residues in peptides is demonstrated by the bromination of the derivatives of valylglycine 17a, glycylvaline 18a, and the cyclic dipeptide 19a to give only the corresponding bromides 17b, 18b and 19b [29, 30]. This selectivity can be exploited in combination with the other effects discussed... 

Dolabella 90 Non-halogenated diterpenes, polypropionates, peptides and cyclic depsipeptides, alkaloids, polypropionates... 

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