Diterpenes, tetracyclic

Kaur-16-en-19-oic acid (625) obtained from Mikania monagasensis inhibited the growth of Staphylococcus aureus and Candida albicans 384). In the latter case, this diterpene was appreciably less active than the co-occurring sesquiterpene lactone, mikanolide. 

The sulfated glycoside, carboxyatractyloside (678), was reported from two sources, Xanthium strumarium 232) and Atractylis gummifera 239). This hypoglycemic compound strongly inhibits translocation of adenine nucleotides 

The role of diterpenes in the resistance of four Solidago (Astereae) species to the beetle Trirhabda (Coleoptera) is under investigation (368). Preliminary results indicate that three of the four kauranoids isolated from the leaves of S. nemoralis and S. altissima, ew/-kauran-16a-ol (720), 15a-hydroxy-eA2/-kaur-16-en-19-oic acid (646), and 17-hydroxy-e /-kaur-15-en-19-oic acid reduced Trirhabda larval growth by 40 percent and adult growth by 32 to 49 percent. The fourth, ew/-kaur-16-en-19-oic acid (625), had no deterrent effect on the larvae and actually stimulated feeding by adults. 

The diterpene alkaloids, lycoctonine (1009) and anthranoyllycoctonine (1010) appear to be responsible for the blood pressure depressant, smooth muscle relaxant and curareform properties of the source plant. Inula royleana (34). 

Salvia przewalskii Lamiaceae 304 Croton sonderianus Euphorbiaceae 305 

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Long-chain ester derivatives of phorbol, a tetracyclic diterpene from the seed oil of Croton tiglium L., including its most abundant representative, 12-0-tetradecanoylphorbol-13-acetate (65), are potent activators of protein kinase G (PKG) and are used as standard tumor promoters for the study of experimental carcinogenesis in animal models." ... 

All GAs are tetracyclic diterpene acids they can be divided into two types, the CpcrGAs and the C n-GAs (Figure 1). 

We ve classified more than 550 diteipenoids (listed in Table 3 whith corresponding sources) from all the reported Salvia species which we ve divided into 2 categories. The first one contains the monocyclic and bicyclic diterpenoids including labdanes and clerodanes and related diterpenes. The second category concerns tricyclic and tetracyclic diterpenes including pimaranes and abietanes and related diterpenes. The clerodane type diterpenes are mainly represented by american species while abietane type are found in european and asian species. 

The cyclization of polyolefin terpenes occurs readily once they have been converted into terminal epoxides. The tetracyclic diterpenes 3a- and 3/S-kaurene have been prepared enzymically from chemically synthesized (/ ,5)-14,15-oxidogeranylgeranyl pyrophosphate (42), providing another example of this cyclization. Trimethyl-aluminium can promote the non-enzymic cyclization of the diethyl ester of neryl phosphate (43), presumably a carbonium ion, to 4-t-butyI-l-methylcyclohexene. ... 

Two groups have reported syntheses of the bicyclo[3.2.1]octane ring system found in certain tetracyclic diterpenes in which the key step is an intramolecular carbenoid insertion reaction. Thus decomposition of the diazoketone (4) in the presence of copper(II) sulfate gives the cyclopropyl ketone (5) in 48% yield. Acid hydrolysis of the acetal grouping is accompanied by concomitant fragmentation to the substituted bicyclo[3.2.1]octanone derivative (6).3... 

Kauranes and Gibberellic Acids.— The parent tetracyclic diterpene from which the gibberellic acids are derived, is enf-kaurene (62). Several workers have... 

Dihydropyran rearrangements [ 1,4 rearrangements] are known to proceed through a boatlike transition state due to the short tethered chain (see p 3337). If a stereogenic center is attached to the new bond, the product stereochemistry is only governed by the substrate configuration, as shown by the synthesis of the precursor 8 of tetracyclic diterpene ( )-aphidicolin613,614. 

Snider was interested in the synthesis of tetracyclic diterpenes. For that purpose, he examined the radical cyclization of tetraene precursor 55 to give highly valuable intermediate 56 for the total synthesis of isosteviol and beyer-15-ene-3,19-diol (Scheme 19). After the initial 6-enr/o-trig cyclization, a subsequent i-endo-ing cyclization involving the unsubstituted ene partner was responsible for the erosion of the yield [33]. 

JtWimeth y f- 8, f /a metham> i taH cyclohepta[a naphthti-teM<9-dimcthanoU I Cl 69653 NSC-234714, CMHMC4 mol wt 338,49. C 70.97%, H 10.12%, O L8,9l%. Novel tetracyclic diterpene antibiotic with antiviral and antimitotic properties, isolated from Cephalosporium aphidicola Fetch, It is a specific inhibitor of DNA < -polymerase. Description and K-ray crystallographic dele ruin of structure K. M. 

Hayashi, T. Kawasaki, M. Miwa, Y. Taga, T. Morita, N. Antiviral Agents of Plant Origin. III. Scopadulin, A Novel Tetracyclic Diterpene from Scoparia dulcis. Chem. Pharm. Bull. 1990, 38, 945-947. 

Of the 72 gibberellins identified by gas chromatography-mass spectrometry (GC-MS), eleven are found only in the ftmgus, G. fuiikuroi. forty seven in higher plants while fourteen additional GAs are common to both groups. The gibberellins are tetracyclic diterpene acids, having in common the carbon skeleton,... 

Mad honey. Common name for Rhododendron honey containing tetracyclic diterpene toxins ( grayanotox-ins) that can lead to atropine-like poisonings. 

Taxoids. Synonymously used term for certain tetracyclic diterpenes ( taxanes) generally all taxanes, which bear oxygen functional groups. 

Many different mono-, bi-, tri-, and tetracyclic diterpenes are found and their formation may be rationalized by acid-catalyzed, stereospecific cyclizations of geranylgeraniol and analogs to yield a variety of diterpene skeleta. Similar processes are assumed to occur in vivo. 

Most tetracyclic diterpenes possess the 53,10a-configu-ration, such as occurs in nr-kaurene (37) (Fig. 22.13), and intermediate in the bios)mthesis of gibberellins. These compounds appear to be widely distributed, but are common in the Euphorbiaceae (especially in Beyeria), the Asteraceae (e.g., Stevia) and gymnosperms. 

B.A. SoLHEiM, J. Clardy, F.G. Pilkiewicz, I. Miura, S.P. Tanis, and K. Nakan-iSHi Kempene-1 and -2, Unusual Tetracyclic Diterpenes from Nasutitermes Termite Soldiers. J. Amer. Chem. Soc. 99, 8082-8083 (1977). 

J.W. Lauher, and M.S. Collins Two New Tetracyclic Diterpenes from the Defense Secretion of the Neotropical Termite Nasutitermes octopilis. Tetrahedron Lett. 3827-3830 (1979). 

M. Tempesta, and C. Turner Longipenol. A Novel Tetracyclic Diterpene from the Termite Soldier Longipeditermes longipes. Tetrahedron Lett. 25, 1531-1532 (1984). 

Kametani and co-workershave used the intramolecular cyclization of the benzocyclobutene (298) to give (299) in a nover synthetic approach to tetracyclic diterpenes. 

Other examples of the use of intramolecular Diels-Alder reactions in preparative chemistry have appeared the o-quinodimethane (186), produced as a transient intermediate in the pyrolysis of the analogous benzocyclobutene, cyclizes to give (187 65%), the desulphurization of which (Raney nickel) affords a potential intermediate for the preparation of tetracyclic diterpenes. Elevated temperatures result in the isomerization of (188) into the internal [4 -I- 2] adduct (189) in which it is clear that a cyano-group has acted as a dienophile (189) is the result of a subsequent double-bond shift, and the structure was validated by crystallographic structure analysis. Bridged y-lactams have been successfully prepared by the intramolecular Diels-Alder reactions of NN-diallyl- and iV-(l,l-dimethylprop-2-yn-l-yl)amides of various penta-2,4-diene carboxylic acids. Thus, pyrolysis of (190) gave an 80%... 

Kaurene ent-kaur-16-ene, a tetracyclic diterpene found in the plant kingdom in both the (+) and (-) forms. (-)-K. M, 272, m.p. 50°C, [a] -75°. There are various stereoisomers of K., some of them occurring naturally. The formula and significance of K. as an intermediate in the biosynthesis of the gibberellin phytohoimones are given under Gibberelli ... 

Prestwich, G. D., Spanton, S. G., Lauher, J. W., Vrkoc, J. (1980) Structure of 3a-hydroxy-15-rippertene. Evidence for 1,2-methyl migration during biosynthesis of a tetracyclic diterpene in termites. J. Am. Chem. Soc, 102, 6825-8. 

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