Biological Activity of Diterpenes

Various biological activities (Table 13 [pp. 489-490]) have been reported for plant diterpenes, principally from members of the Ericaceae, Euphorbiaceae, Lamiaeeae, and Compositae. Each of the major diterpenoid classes from this last family will be discussed below in terms of its biological properties. 

For hundreds of years, a tea brewed from the leaves of Montanoa tomentosa has been used medicinally to induce labor and as an antifertility agent (419, 382). The M. tomentosa extract possessed abortifacient, labor induction, and menstruation induction effects (572, 297). Zoapatanol (55) appears to be the tea component responsible for most of the activity (368). In addition to zoapatanol, several other oxepane diterpenes (56, 57, 1097, 1098, 1099) and their uncyclized precursors (1094, 1095, 1096) were isolated from this species. Commercial interest in these compounds has led to the synthesis of analogous structures sharing similar pharmacological properties (353). 

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The biological activity of diterpenes is copiously reported in the literature. Singh et al. reviewed the biological activity of labdane diterpenes from 1987 to 1997.30 The antibacterial, antifungal, anti-inflammatory, cytotoxic and other... 

Marston A, Hecker E 1984 Isolation and biological activities of diterpene anthraniloyl and 3-hydroxyanthraniloyl peptide esters from Euphorbia milii. Progress In Tryptophan And Serotonin Research. Walter de Gruyter and Co., Berlin p. 789-792... 

Chemical Structures and Biological Activity of Natural Diterpene QMs... 

The stmctural complexity and biological activity of the cyathane family of diterpenes has stimulated considerable interest from synthetic chemists, as reflected in the number and diversity of approaches reported thus far [42]. Our own strategy for cyathane synthesis is based on a rhodium-catalyzed [5+2] cycloaddition. The precursor for this reaction was fashioned ultimately from commercially available and inexpensive (S)-(-)-limonene. Treatment of the ketone 139 with 5 mol% [RhCl(CO)2]2 in 1,2-dichloro-ethane gave cycloadduct 140 (Scheme 13.14) in 90% yield and in analytically pure form after simple filtration through a plug of neutral alumina [43]. 

An intramolecular 2-alkylation was also observed in a sulfonyl free radical induced addition-cyclization <95SL763>. A key intermediate in a new synthesis of pallescensin A (a biologically active labdane diterpene) was prepared by a cationic cyclization reaction with a furan <95SYN1141>. The sonochemical Barbier reaction was extended to carboxylate salts. 2-Furanylketones 10 can be obtained by sonication of a mixture of furan, lithium carboxylate, an alkylchloride, and lithium in THF <95JOC8>. 

Even though much is already known about the toxicity of diterpene alkaloids that contribute to the toxicity of Consolida, Delphinium, and Aconitium species, no antiviral study has been so far reported on this type of alkaloids. Therefore, no SAR studies have been encountered by us on the antiviral or antimicrobial activities of these alkaloids. However, a quantitative SAR analysis performed on a number of diterpene alkaloids isolated from an Aconitum sp. indicated that biological activity of these alkaloids may be related to their toxicity rather than to a specific pharmacological action [40]. In a current study on 43 norditerpenoid alkaloids from Consolida, Delphinium, and Aconitum species against several tumor cell lines, lycoctonine and browniine were... 

We have described the chemistry of some selected sesquiterpenes which have been classified as phytoallexins. We would to apologize for unintentional omission of any important information in this review, which we tried to make as comprehensive as possible. A variety of synthetic reactions has been used to achieve the total synthesis of these phytoalexin sesquiterpenes. The isolation and biological activity of these sesquiterpenes have been discussed. It is necessary to mention that Takasugi et al.81 have reported for the first time costunolide is an antifungal sesquiterpene which inhibited spore germination of Ceratocystis fimbriata at concentration of 32 pg/ml. Many diterpenes and flavonoides have been also listed as phytoallexins. It is hoped that the research workers would find some useful information in this article. It is safe to predict from discussions in this article that many organic chemists would try to isolate antifungal sesquiterpenes. 

Diterpenes are known to play diverse roles in plants. The ubiquitous acyclic compound, phytol (4), is a part of the chlorophyll molecule and is essential to photosynthesis. The biological activity of gibberellins (such as 41) as plant hormonal substance is discussed above. 

Phillipson JD, Wright CW, Kirby GC, Wrhurst DC (1995) Structure and biological activity of sesquiterpene and diterpene derivatives horn medicinal plants. In Hostettmann K, Marston A, Maillard M, Hamburger M (eds) Phytochemistry of the plants used in traditional... 

Also the clerodane class of diterpenes exhibited a wide range of biological activities. Of particular interest is asmarine A and B (9) [22] that showed antiproliferative activity against several human cancer cell lines and, clerocidin (10) [23], a naturally occurring antibiotic showing also anticancer... 

The chromane ring is derived from the diterpenic alcohol phytol, with the systematic name (2 ,7 ,11 )-3,7,11,15-tetramethylhexadec-2-en-l-ol, but in addition to the hydroxyl groups in position C-6 it contains another methyl group at position C-2. The presence of these functional groups is essential for the biological activity of all vitamers. Four forms of vitamin E with a saturated terpenoid side chain derived from the tocol are called tocopherols (5-33) four forms with unsaturated... 

Diterpenic alcohols Diterpenic alcohols are present in nature as free compounds or bound in fatty acid esters and glycosides. They have no significance as flavourings, but may be precursors of flavour-active products. A number of diterpenoids are biologically active substances. Diterpenic alcohols known as gibberellins are found universally in plant tissues, and act as plant hormones. 

The TMM [4-1-3] cycloaddition to pyrone has been employed in a synthetic study of a novel biologically active diterpene pseudolaric acid B (106), in which the formation of the bridged adduct (107) from the 2-pyrone (108) is the key step in the sequence (Scheme 2.29). A mixture of the other isomer (109) and the methylenecyclopentane (110) was also isolated from the reaction. It is important to point out that the presence of a tin co-catalyst is critical in effecting the reaction. This is the first example a "tin-effect observed in a [4-1-3] cycloaddition [40]. 

The tricyclic substance 18A and 18B are both potential synthetic intermediates for synthesis of the biologically active diterpene forskolin. These intermediates can be prepared from the monocyclic precursors shown. Indicate the nature of the reactions involved in these transformations. 

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