Halogenated natural products

In the biosynthetic schemes proposed for some halogenated natural products, positive halogen intermediates are attacked by electrons from the n bond of an alkene or alkyne in an addition reaction. 

S., Vatter, S., Chahbane, N., Lenoir, D., Schramm, K.W. and Scherer, G. (2005) Biological activity and physicochemical parameters of marine halogenated natural products 2,3,3, 4,4, 5,5 -heptachloro-l -methyl-1,2 -bipyrrole and 2,4,6-tribromoanisole. Archives of Environmental Contamination and Toxicology, 48, 1-9. 

Vetter W (2006) Marine Halogenated Natural Products of Environmental Relevance. Rev Environ Contam Toxicol 188 1... 

Vetter W, Janussen D (2005) Halogenated Natural Products in Five Species of Antarctic Sponges Compounds with POP-Like Properties Environ Sci Technol 39 3889... 

Hiebl J, Melcher J, Gundersen H, Schlabach M, Vetter W (2006) Identibcation and Quantihcation of Polybrominated Hexahydroxanthene Derivatives and Other Halogenated Natural Products in Commercial Fish and Other Marine Samples. J Agric Food Chem 54 2652... 

Vetter W, Jun W, Althoff G (2003) Non-Polar Halogenated Natural Products Bioaccumulated in Marine Samples. I. 2,3,3 ,4,4 ,5,5 -Heptachloro-l -methyl-l,2 -bipyrrole (Ql). Chemosphere 52 415... 

Vetter W, Stoll E, Garson MJ, Fahey SJ, Gaus C, Muller JF (2002) Sponge Halogenated Natural Products Found at Parts-Per-Million Levels in Marine Mammals. Environ Toxicol Chem 21 2014... 

Halogenated natural products are mainly known from marine organisms, fungi and higher plants. The halogenated structures isolated from liverworts should, of course, have chemotaxonomical significance. 

For example, termites produce up to 15% of the global chloroform emissions,68 most likely by a Haloform reaction. Halogenated ketones are ubiquitous in the oceans and a few examples are shown (27-30).66 The antibacterial tribromoacetamide is present in an Okinawan Wrangelia alga,69 and myriad other halogenated natural products can be envisioned to produce haloform.66... 

The reason behind this is the easy oxidation of bromide ion into bromine or bromonirtm ion or biological equivalent [3]. There are many halogenated natural products known in literature that have been reviewed [4-7]. However, to the best of our knowledge, none of the review exclusively dedicated for the marine brominated alkaloids is reported in literature. 

The biosynthesis of certain halogenated marine natural products is intriguing. Some of their halogens appear to have been introduced as electrophiles rather than as Lewis bases or nucleophiles, which is their character when they are solutes in seawater. But how do marine organisms transform nucleophilic halide anions into electrophilic species for incorporation into their metabolites It happens that many marine organisms have enzymes called haloperoxidases that convert nucleophilic iodide, bromide, or chloride anions into electrophilic species that react like F, Br, or CF. In the biosynthetic schemes proposed for some halogenated natural products, positive halogen intermediates are attacked by electrons from the 77 bond of an alkene or alkyne in an addition reaction. 

Halogen-containing compounds are not only produced by man, but also by Nature [1740-1742], A brominated indole derivative - Tyrian purple dye - was isolated from the mollusc Murex brandaris by the Phoenicians. Since that time, more than 1,000 halogenated natural products of various structural types have been isolated from sources such as bacteria, fungi, algae, higher plants, marine molluscs, insects, and mammals [1743], Whereas fluorinated and iodinated species are rather rare, chloro and bromo derivatives are found more often. The former are predominantly... 

Vetter, Walter, Marine Halogenated Natural Products of Envuonmental Relevance, Reviews of Environmental Contamination and Toxicology, 188, 1-57 (2006). 

STEREOSEI CnVE SYNTHESIS OF HALOGENATED NATURAL PRODUCTS... 

Nature has effectively designed chemical events that produce halogenated compounds by both ionic and radical pathways. Cyclic halogenated natural products are produced by the electrophihc activation of olefins and the subsequent capture of the resultant cationic species by a nucleophilic motif of the molecules. The stereochemical... 

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