Sponge-derived natural products

An intriguing application of Zincke processes occurred in Marazano s synthesis of dimeric, tetrameric, and even octameric pyridinium macrocycles, including cyclostellettamine B, a sponge-derived natural product. The same strategy produced a synthesis of haliclamine A (121, Scheme 8.4.41), a cytotoxic sponge metabolite. Intermediate 119, itself produced via a Zincke route, underwent an intramolecular Zincke reaction, providing macrocycle 120, which was reduced to the natural product. 

Thus, research concentrated on the synthesis of these biologically active sponge-derived natural products among many others, the total synthesis of peroxyacarnoates A and D 224 and 225, which show exceptional activity against fungal and cancer cell lines, has been published <20050L2509>. 

Orhan, 1., Sener, B., Kaiser, M., Brun, R., and Tasdemir, D. (2010) Inhibitory activity of marine sponge-derived natural products against parasitic protozoa. Mar. Drugs, 8, 47-58. 

The list of natural product similarities from land and the sea is immense, with metabolites of all chemical classes. On land these mostly derive from bacteria, cyanobacteria, plants, fiingi, insects, amphibians, and mammals in the sea, besides bacteria and cyanobacteria, the sponges, cnidarians, bryozoans, moUusks, ascidians, and sharks produce most. The ascidians are exclusively marine, and the sponges, cnidarians, and bryozoans are productive only in the sea. Dietary metabolites are also... 

The relative contribution to the cup of natural products by marine and terrestrial organisms is outlined in Table 9.1. Column entries are the phylum, class or order, number of species, biogenetic class of metabolites produced, their bioactivity level, and a qualitative indication as to the average molecular complexity (Whitlock 1998). The latter property receives closer attention in Table 9.II for specific molecular skeletons. These data warrant several conclusions. First, unusual secondary metabolites on land derive mostly fi-om green plants and arthropods, while in the sea are the algae, sponges, cnidarians, bryozoans, and ascidians that give most. This is true no matter if the molecular skeleton, or the actual metabolite, or even the bioactivity, is examined. 

The chemistry of fiiians and benzofurans was a Held of lively research in the last year. There are a number of reasons for this activity. The furan ring system - both in its native as well as in its reduced form - occurs in a great number of natural products and a wide variety of these compounds has been isolated from natural sources. This subject is treated regularly with care and accuracy in Heterocycles and will not be repeated here. Therefore only a few examples will be given in this chapter. Several new furan derivatives were isolated from natural sources (-)-wistarin 1 from the marine sponge Ircinia sp. <99TA3869>,... 

Sponges are considered as the chemical factory in marine environment because of its immense production of chemically diverse compounds. Other than the chemical diversity, these compounds possess remarkable bioactivities. This great potential has aroused applications of sponge-derived compounds as therapeutics and at present, a number of promising compounds are in clinical and preclinical trials. Recently, nutraceuticals have received considerable interest among the health conscious community because of its multiple therapeutic effects. Natural health-promoting substances... 

Cyclotheonamide A (CtA), a macrocyclic marine natural product derived from the Japanese sponge, Theonella sp., inhibits thrombin with an IC50 value of... 

The marine isothiocyanates, with more than 80 compounds isolated so far, form the largest group of naturally occurring isothiocyanates. This well-established group of marine natural products is constituted mainly by terpene metabolites present as sesquiterpene and diterpene derivatives. The non-terpene isothiocyanate compounds include two cylindricine alkaloids and a series of long-chain aliphatic metabolites. Marine sponges constitute the main source of these compounds, although they are also found in nudibranches and tunicates. 

Mamanulhaquinone (1) is a combination of a sesquiterpene and a quinone. Its skeleton, with both terpene and quinone or hy-droquinone portions, is not unusual for a natural product derived from a sponge.2 An example is avarol (2). containing a hydroqui-none ring and the terpene skeleton of drimane.3... 

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