6,12-Guaianolides

Guaianolides Anthemis carpatica SiOj Multicomponent eluents — Identification 70 ... 

Substituted furan formation by an indirect cyclization of 1,4-dicarbonyl derivatives has also been adopted as a key step in the synthesis of 3-oxa-guaianolides. Although 1,4-dicarbonyl compounds have been traditionally considered as the direct precursors for furans, treatment of 1,4-dicarbonyl compounds having a tertiary acetoxy group with p-toluenesulfonic acid leads to only 11% yield of an alkenylfurans as derived from a cyclization/acetoxy-elimination route. The following scheme shows an alternative multi-step conversion of the 1,4-dicarbonyl that leads to a more acceptable yield of the acetoxyfuran . 

Macias LA, Varela RM, Torres A, Mohnillo JMG (1993) Potential allelopathic guaianolides from cultivar sunflower leaves, var. SH-222. Phytochemistry 34 669-674 Macias LA, Molinillo JMG, Galindo JCG, Varela RM, Simonet AM, Castellano D (2001) The use of allelopathic studies in search for natural herbicides. J Crop Prod 4 237-256 Macias AL, Marin D, Oliveros-Bastidas A, Varela RM, Simonet AM, Carrera C, Molinillo JM (2003) Allelopathy as a new strategy for sustainable ecosystems development. Biol Sci Space 17 18-23... 

In summary, feverfew appears to be a source of a range of sesquiterpene lactones of three different types germacranolides, eudesmanolides and guaianolides. 

A few individual terpenoids, as well as less expensive mixtures of these compounds, find practical applications. Some examples are the tli terpenoid Vitamin A, the sesquiterpenoid santonin (as an anthelmintic), and the pyrcthnns, pyrctholonc esters of the monoterpenoid chrysanthcmic acid (used as an insecticide). A number of sesquiterpenoid lactones of the germacranolide. guaianolide and elemanolide types have shown promise as rumor inhibitors. 

In addition to the myriad natural marine halogenated sesquiterpenes (vide infra), the terrestrial plant kingdom is also a major source of halogenated (chlorinated) sesquiterpenes, most of which possess the guaianolide skeleton (498). 

Although the first survey listed 45 natural chlorinated sesquiterpene lactones, several such compounds were omitted in that coverage (1) and are described here. The novel sesquiterpene lactone chlorochrymorin (239) was isolated from Chrysanthemum morfolium (499), and the chlorohydrin graminichlorin (240) is found in Liatris graminifolia (500). The antibacterial AA-57 (241), which is related to pentalenolactone, is produced by a Streptomyces sp. (501). The plant Eupatorium chinense var. simplicifolium has yielded eupachifolin D (242) (502) (side-chain double bond stereochemistry revised (518)), and the new guaianolide andalucin (243) was characterized from Artemisia lanata (503). The previously known chlorohyssopifolins (1) have been studied for cytostatic activity, and the presence of one and even two chlorine atoms amplifies this activity (504). 

Examination of the Montenegro Achillea clavennae reveals the presence of three new chlorine-containing guaianolides 277-279 in addition to several known analogues (524). The first investigation of the Chinese medicinal plant Vernonia chinensis has uncovered the new chlorinated sesquiterpene lactones vemchinilides A (280), B (281), C (282) and E (283) (525). Vemchinilides B and E exhibit potent cytotoxic activity against the P-388 and A-549 cell lines. The structurally similar vemolide C (284) was found in the Cambodian traditional medicinal plant Vernonia cinera (fever, colic, malaria) (526). Indeed, vemolide C could be identical with vemchinilide A. 

Herz W, Poplawski J, Sharma RP (1975) New Guaianolides from Liatris Species. J Org Chem 40 199... 

Oksiiz S, Topcu G (1994) Guaianolides from Centaurea glastifolia. Phytochemistry 37 ... 

Ahmed AA, Gati T, Hussein TA, Ali AT, Tzakou OA, Couladis MA, Mabry TJ, Toth G (2003) Ligustolide A and B, Two Novel Sesquiterpenes with Rare Skeletons and Three 1,10 -seco-Guaianolide Derivatives from Achillea ligustica. Tetrahedron 59 3729... 

Bentamene A, Benayache S, Creche J, Petit G, Bermejo-Barrera J, Leon F, Benayache F (2005). A New Guaianolide and Other Sesquiterpene Lactones from Centaurea acaulis L. (Asteraceae). Biochem Syst Ecol 33 1061... 

Macias, F.A., Galindo, J.C.G., Castellano, D., Velasco, R. Sesquiterpene lactones with potential use as natural herbicide models. 2. Guaianolides. J Agric Food Chem 2002a 48 5288-5296. 

Active Constituents Absinthine (a dimeric guaianolide), anabsinthin, and a volatile oil mainly consisting of thujone. 

Differences in activity are observed when a double bond is present or not in the lactone ring.13,25 However, several compounds without an a,(3-unsaturated-y-lactone system present higher levels of activity than GR-24. This is true for dihydroparthenolide (56) and the guaianolides 68 and 69. As these compounds cannot react in a Michael addition fashion, other recognition mechanisms different from that proposed by Zwanenburg31 could be operating in this case. 

Thirty-six plant species tested in cell suspension culture could be elicited by exogenously supplied methyl jasmonate to accumulate secondary metabolites by a factor of 9 to 30 over the control values. Induction by MJ was not specific to any one type of secondary metabolite but rather general to a wide spectrum of low molecular weight substances ranging from flavonoids, guaianolides and anthraquinones to various classes of alkaloids [96]. Endogenous jasmonic acid and its methyl ester (MJ) accumulate rapidly and transiently after treatment of plant cell suspension cultures of Rauvolfia canescens and Eschscholtzia califor-nica with a yeast elicitor [97]. 

From six-membered rings Rearrangement as part of the pseudo-guaianolide to confertin synthesis [14]. 

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