Secondary diterpene metabolites

Stypodiol, epistypodiol and stypotriol are secondary diterpene metabolites produced by the tropical brown algae Stypopodium zonaie. These compounds display diverse biological properties, including strong toxic, narcotic, and hyperactive effects upon the reef-dwelling fish. In the laboratory of A. Abad an efficient stereoselective synthesis of stypodiol and its C14 epimer, epistypodiol, was accomplished from (S)-(+)-carvone. The key transformations in the synthesis of these epimeric compounds were an intramolecular Diels-Alder reaction, a sonochemical Barbier reaction and an acid-catalyzed quinol-tertiary alcohol cyclization. 

The typical secondary metabolites of soft corals are diterpenoids, although some species also produce sesquiterpenoids. Despite the fleshy nature of soft corals relative to other invertebrates, predation is rare because the diterpene metabolites produced are believed to be potent feeding deterrents.138... 

Crinitol, (1), is a diterpene diol whose properties can in some ways be taken as representative of the current challenges in studying and finding uses for secondary plant metabolites. It is readily availability from a natural source and has a relatively uncomplicated structure despite this, its function in the plant is not fully clarified. As will be discussed below, crinitol shows a modest level of antimicrobial and other biological activity. We can already control many troublesome microorganisms that contaminate food and cosmetics with natural products, including plant secondary metabolites, that are currently available. Nevertheless, discovery... 

In 1992, Paul and Van Alstyne reported on the processes that occur after tissue disruption in different species of the calcified green seaweed Halimeda [56]. After wounding, these algae transform their major secondary metabolite, the his-enoylacetate diterpene halimedatetraacetate (48), into halimedatrial (50) and epihalimedatrial (51). The structural relationship between the educt and the reaction products suggests that the transformation occurs by a combination of solvolysis and hydrolysis reactions as indicated in Scheme 14 [108]. 

A recent example demonstrates that corals rely on induced biosynthesis of terpenes as a dynamic defense strategy as well. The induction of terpenoid secondary metabolites was observed in the sea whip Pseudopterogorgia elisabethae [162]. Levels of pseudopterosins 89-92, a group of diterpene glycosides with anti-inflammatory and analgesic properties (Scheme 23) [163-165], are increased in response predation by the mollusk Cyphoma gibbosum. First bioassays indicate that these natural products are involved in the chemical defense. 

Low susceptibility to reef fishes in Florida and produces secondary metabolites (Paul and Hay 1986). Crude extract from Guam specimens inhibits herbivory by reef fishes (Paul 1987) crude extract and a mixture of two diterpenes inhibits herbivory by the gastropod Astraea latispina (Pereira et al. 2002)... 

Schmitt TM, Lindquist N, Hay ME (1998) Seaweed secondary metabolites as antifoulants effects of Dictyota spp. diterpenes on survivorship, settlement, and development of invertebrate larvae. Chemoecology 8 125-131... 

Phytochemical studies of these species led to the isolation and structural characterization, by NMR and MS analysis, of many secondary metabolites, mainly flavonoids, and expecially flavonol glycosides, clerodane diterpenes, and triterpenes having the lupane, ursane, and oleanane skeletons. Particularly flavonoids and their glycosides have a chemotaxonomic interest in the genus and in general in the Chrysobalanaceae family. 

In the course of our phytochemical work we studied seven Licania species all belonging to Venezuelan flora, collected in Puerto Ayacucho, Estado Amazonas and in the Parque Nacional Henry Pittieri, Maracay, Estado Aragua. A number of new and known secondary metabolites, mainly flavonoids, especially flavonol glycosides, sterols, and triterpenes having the lupane, ursane, and oleanane skeleton were isolated and characterized. The last part of this chapter deals also with the isolation of clerodane diterpenes from the methanol extract of L. intrapetiolaris by Oberlies et al., 2001 [4]. All the Licania species investigated up to now are reported in Table 1. 

Biologically active secondary metabolites from fungi. 12. Oidiolactones A-F, labdane diterpene derivatives isolated from Oidiodendron truncata. John, M. Krohn, K. Florke, U. Aust, H-J. Draeger, S. Schulz, B. J. Nat. Prod. 1999, 62, 1218-1221. 

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