Sesterterpenoid

A 1,2-metalate rearrangement of a higher order cuprate, known as a Kodenski rearrangement [64], was used as a key step in the synthesis of the marine antiinflammatory sesterterpenoid manoalide 95 (Scheme 9.20) [65]. Treatment of the alkenyl lithium 89 (prepared from the alkenylstannane 88 with s-BuLi in a diethyl ether-pentane mixture) with the homocuprate 91 (produced from iodoalkane 90) gave the iodoalkene 94 in 72% overall yield from 88. The reaction proceeds as fol-... 

Sponge-derived sesterterpenoids are potent anti-inflammatory metabolites which inhibit phospholipase A2 (Sipkema et ah, 2005a). In arachi-donic acid pathway of inflammatory response (Fig. 8.3), phospholipase A2 catalyzes the release of membrane-bound phospholipids to produce inflammatory mediators once stimulated by tissue injury. Manoalide (Fig. 8.4) is a best known sponge-derived anti-inflammatory sesterterpe-noid. Dysidotronic acid (Fig. 8.5), non-complex manoalide analogue, has been identified as an anti-inflammatory metabolite of the sponge Dysidea sp. The mechanism by which dysidotronic acid inhibit inflammation is much more selective and potent than manoalide. This sesquiterpenoid... 

Additionally, during the search for biologically active sponge metabolites belonging to the sesterterpenoid class, a sulfated sesterterpene hydroquinone, halisulphate, Fig. (20), was isolated from the dark brown sponge Halichotidriidae sp. 

Manoalide, a marine anti-inflammatory sesterterpenoid, has been synthesized555 using a 1,2-metallate rearrangement of a higher order cuprate and a Pd(0)-catalysed carbonylation of an iodoalkene to generate the central dihydropyranone ring. 

Cimino, G., Fontana, A., Giminez, F., Marin, A., Mollo, E., Trivellone, E., and Zubia, E., Biotransformation of a dietary sesterterpenoid in the Mediterranean nudibranch Hypselodoris orsini, Experi-entia, 49, 582, 1993. 

De Silva, E. D., and Scheuer, P. J., Manoalide, an antibiotic sesterterpenoid from the marine sponge Lujfariella variabilis (Polejaeff), Tetrahedron Lett., 21, 1611, 1980. 

Idiadione (56) was synthesized from citronellal, establishing the stere-ogenic center as S [31], Cytotoxic sesterterpenoid cacospongionolide D (57) was isolated from Fasciospongia cavernosa from the Bay of Naples [32]. Thorectolide monoacetate (58), obtained from a New Caledonian marine sponge identified as a Hyrtios species [33], in contrast possessed antiinflammatory properties. The bicyclic lactone astakolactin (59) was obtained... 

During their studies on the stereochemistry of intramolecular 1,3-diyl trapping reaction as depicted in Scheme 13, Little and collaborators utilized the reductive decarboxylation in preparing the required compound 31.24 The usefulness of Barton decarboxylation was also realized by Braekman and colleagues during their studies on ichthyotoxic sesterterpenoids in providing the needed methyl ketone 32 from the carboxylic acid 33.25 Helmchen has developed an easy route to a stable... 

Tables 2-5 list monoterpenoids (Mo), sesquiterpenoids (Sq), diterpenoids (Di), and retinoids (Re), sesterterpenoids (St), meroterpenoids and miscellaneous terpenoids (Me), respectively, discussed in this review. The bioassay systems in which the compounds exhibited inhibitory effects, together with the major sources of the compounds, are included in the Tables. Most of these terpenoids are isolated from natural sources, and their structures are shown in Figs. (2)-(5). Some terpenoids which exhibit significant and/or a broad range of chemopreventive and anti-inflammatory activities are discussed below.

Table 5. Retinoids (Re), Sesterterpenoids (St), and Miscellaneous Terpenoids from Natural Sources and the Bioassay Systems in which the Compounds Exhibited Inhibitory Activities Code Compound Source Occurrence Assay System References...

Fig. (5). Structures of retinoids, sesterterpenoids, meroterpenoids, and miscellaneous terpenoids described in this review...

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