Sesquiterpenes isolation

Longifolene in its dextrorotatory form is a sesquiterpene isolated by Simonsen from Indian turpentine oil from Pinus longifolia. It is a colourless viscous liquid having the following characters —... 

Shimomura, O. (1989). Chemiluminescence of panal (a sesquiterpene) isolated from the luminous fungus Panellus stipticus. Photochem. Photobiol. 49 355-360. 

Sample Site n Head Sesquiterpene ISOL COSA ILLA COST TULP ... 

Parallel studies of extracts and mixtures of compounds isolated from ragweed, Ambrosia artemisiifolia L., were also made. Water extracts of ragweed proved highly inhibitory of seed germination. Mixed sesquiterpenes isolated from ragweed were very inhibitory of onion, oat, ryegrass, and Palmer amaranth germination when applied in a dichloromethane solution pretreatment. 

Pettersen RG, Gullen DL, SpitderTD, Kingston DGI, The crystal and molecular structure of fluorensadiol, a natural product sesquiterpene isolated from a west Texas daxxLo, Acta Crystallogr Sect B Struct Sci 3 24— 27, 1975. 

Artemisinin is a natural endoperoxide-containing sesquiterpene, isolated from a plant used in traditional Chinese medicine. Acetalic artemisinin derivatives (arte-mether, artesunate) are very active against chemo-resistant forms of Plasmodium falciparum, and are clinically used for the treatment. However, they suffer from an unfavourable pharmacological profile. They are quickly metabolised by fast oxidative metabolism, hydrolytic cleavage and glucuronidation. 

Occidentalol (628), a eudesmane-type sesquiterpene isolated from the wood of Eastern white cedar, was synthesized from a as-fused decalin system (627) prepared by cycloaddition of the a-pyrone (625) with 4-methyl-3-cyclohexenone (626 Scheme 140) (72TL4651). Derivatives of 2-pyrone have also been employed in syntheses of colchicine (629 Scheme 141) (59AG637) and barrelene (630 Scheme 142) (69JA2330). 

Muto, S., Bando, M. and Mori, K. (2004). Synthesis and stereochemistry of the four himachalene-type sesquiterpenes isolated from the flea beetle (Aphthona flava) as pheromone candidates. Eur. J. Org. Chem., 2004,1946-1952. 

Si4.6 whereas a silicon-based approach proved to be successful and gave the required exocyclic double bond in (3-Gorgonene, a non-isoprenoid sesquiterpene isolated from Pseudopteragorgia americana. The success of the a-silyl carbanion here is attributed to the lengthy carbon-silicon bond which makes the carbanion sterically less demanding. 

A series of new examples has recently emerged in the literature. Aquaticol (10), an unusual cuparane-type bis-sesquiterpene isolated from the medicinal plant Veronica anagailis-aquatica, can be derived from a Diels-Alder cyclodimerization of the ortfco-quinol 11, itself derived from an enantiospecific oxidative hydroxylation of (—)-d-cuparenol (12) (Figure 5) [37, 38]. Sorbicillinoid members of the vertinoid polyketide class of natural products also present the same chemical filiation inasmuch as they appear to originate biosynthetically from the sorbicillinol (13)-derived ortho-quinol 14 (Figure 6) (Section 15.3.3) [39, 40]. 

A summary of the different sesquiterpenes isolated from the extracts of various plant parts of star anise is shown in Table 17.4. 

Hernandulcin is a bisabolane sesquiterpene isolated from the herb Lippia dulcis Trev. (Verbenaceae), which is native to Mexico, and has been reported to be 1500 times sweeter than sucrose.44 45 The natural product has a 6S, 1 xS" configuration, and of the four possible stereoisomers, only this one has intense sweetness.46 47 Another sweet substance, 4,3-hydn> x v hern a n d u I cm, was isolated from a sample native to Panama.46 The sweetness and bitterness of hernandulcin have been reported to linger in the mouth for sometime. This compound is rather thermolabile. 

On the basis of this palladium-mediated three-component coupling reaction, Morimoto and co-workers developed a methodology for the synthesis of two novel modified furanoeremophilane-type sesquiterpenes isolated from Trichilia cuneata, the 13-hydroxy-14-nordehydrocacalohastine 72 and 13-acetoxy-14-nordehydrocacalohastine 73 [75]. These two natural products showed inhibitory activities for membrane lipid peroxidation in mitochon-... 

Illudin M (46), a toxic sesquiterpene isolated from the jack-o -lantem mushroom, has been synthesized via the same tandem cyclization-cycloaddition strategy involving a-diazoketone 55. The first and key step of the synthesis consisted of a carbonyl ylide 1,3-... 

Ring expansion of the keto ester 148 by flash vacuum thermolysis at 520 °C at 0.01 mmHg afforded the l-benzoxocin-6-one derivative 149 in an excellent yield (95%) (Scheme 38) <2004TL9653>, which was used as intermediate in the synthesis of helianane, a novel heterocyclic sesquiterpene isolated from the marine sponge Haliclona fascigera <1997JOC2646>. 

Ref. 4 in Wakamatsu K, Kigoshi H, Niiyama K, Niwa H, Yamada K (1984) Stereocontrolled Total Synthesis of (+)-Asteromurin A, a Picrotoxane Sesquiterpene Isolated from the Scale Insect Asterococcus muratae Kuwana. Chem Lett 1763... 

Structure 5-3. Structures of sesquiterpenes isolated from A. annua (1972-2004). 

The fascinating lactone isolactarorufin (9.5) (Table 9) is the only example of isolactarane sesquiterpenes isolated from a Lactarius specie (43-45). The structure of isolactarorufin has been elucidated by spectroscopic data and confirmed by X-ray analysis of its p-bromobenzoate 9.8 (45). 

The same authors assigned the structure 11.1 to a new polyunsaturated 5-lactaranolide sesquiterpene isolated from an ethanol extract of L. vellereus (56). 

For the stereoselective total synthesis of bazzanene (12 Scheme 8), a sesquiterpene isolated from the liverwort Bazzania pompeana, the fragmentation of the monoprotected mesylate (10) was used. The mesylate (10) is obtained from the triol (9), an intermediate in the synthesis of gymnomitrane sesquiter-penes. Treatment of (10) with KOBu produces cleanly the expected cyclohexenone (11). 

Fig. (11). Structure of eremophylane-type sesquiterpenes isolated from Senecio aegyptus var. discoideus...

Cemuole is a sesquiterpene isolated from Bidens cernua [168,169]. This compound suppresses in vitro the growth of Gram (+) bacteria and microdermatophytes in concentration of 5-20 mg/1, feebly active as regard to Gram (-) bacteria. 

The total synthesis of (+)-furoscrobiculin B, a lactarane sesquiterpene isolated from basidiomycetes of mushrooms, was accomplished in the laboratory of H. Suemune and K. Kanematsu using a furan ring transfer reaction and a semipinacol rearrangement as key steps. The secondary hydroxyl group of the tricyclic c/s-vicinal diol substrate was converted to the corresponding tosylate that in situ underwent a ring-expansion reaction to afford an azulenofuran in good yield. 

Cacalol (596), a major constituent of Cacalia delfiniifolia Sieb. et Zucc., was oxidized with iodine (1 equiv.) and NaOMe in MeOH to give 11-methoxycacalol (597) in 62% yield. With 2 equivalents of iodine, a similar reaction provided cacalal (598), another sesquiterpene isolated from the same plant, although the yield (0.8%) was very low (Scheme 114). 

Tori. M., Nakashima, K., Seike, M., Asakawa, Y., Wright, A.D., Konig, G.M., and Sticher, O., Revised structure of a brasilane-type sesquiterpene isolated from the red alga Laurencia implicata and its absolute configuration. Tetrahedron Lett., 35, 3105, 1994. 

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