Pyrrole alkaloids, brominated

Most of the known natural brominated pyrrole alkaloids are found in sponges, and several new examples were isolated since the first survey (1). Reviews are available that discuss the occurrence and syntheses of these metabolites (1236-1238). The Papua New Guinea sponge Agelas nakamurai has yielded the new simple pyrroles 1222 and 1223 (1239). The dibromo analog (1224) of 1223 along with enantiomeric lactams 1225/1226, which were separated by chiral HPLC, and... 

Dibromosceptrin (69), tested together with other brominated pyrrole alkaloids for interaction with cellular calcium homeostatis, was shown to reduce voltage-dependent calcium elevation in PC12 cells [113]. 

Bickmeyer, U., Drechsler, C., Kock, M., Assmann, M., (2004). Brominated pyrrole alkaloids from marine Agelas sponges reduce depolarization -induced cellular calcium elevation. Toxicon 44, 45-51. 

This section and the section on alkaloids in the first survey (7) are artificially small since many halogenated alkaloids are presented in the sections on pyrroles, indoles, carbolines, tyrosines, and other nitrogen heterocycles. It might be noted that the very large number of brominated alkaloids that are obviously tyrosine-derived are now included in Sect. 3.22.3 (Tyrosines). 

Some nonbrominated pyrrole-imidazole alkaloids are included in this chapter, but only when they are close analogs of the corresponding brominated compounds. 

A brominated pyrrole-imidazole alkaloid, rac-dibromophakellstatin, has been shown to display selective antitumor activity in vitro with the highest activity on the ovarian cancer cell line OVXF 899L <2007BMCL346>. The chemistry and bioactivity of anti-tubulin agents, either natural or synthetic, having an indole as core nucleus have been reviewed <2007MI209>. 

Bromination of the pyrrole 4-position or of the imidazole part has never been observed. A great molecular diversity is observed in this group of alkaloids extremely varied chemical architectures are reported, ranging from linear oroidin-like monomers to complex polyciclic and tetrameric molecules. In this chapter illustrative structures of this alkaloids family are reported, divided into the following groups ... 

Xu, Y.Z., Yakushijin, K., and Horne, D.A. (1996) Transbromination of brominated pyrrole and imidazole derivatives Synthesis of the CuNs marine alkaloid stevensine. Tetrahedron Lett., 37, 8121-8124. 

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