Sesquiterpene dilactone

Ahmed M, Rahman MT. Alimuzzaman M, Shilpi JA. Analgesic sesquiterpene dilactone from Mikania cordata. Fitoterapia 2001 72 919-921. 

Herz W, Subramaniam PS, Santhanam PS, Aota K, Hall AL. Structure elucidation of sesquiterpene dilactones from Mikania scandens (L.) Willd. J Org Chem 1970 35 1453-1464. 

After these pioneering works, several reviews cover the enormous number of papers published in this field [3-7]. The synthesis of oxetanes can have a great importance in the development of compounds with relevant biological properties oxetane ring is present in the skeleton of taxol (1), an important drug used in the treatment of ovarian cancer [8] in merrilactone A (2), a new sesquiterpene dilactone with neurotrophic activity [9] and in several antiviral oxetanes, such as 3, 4, and 5, which have been described in literature (Scheme 3.2) [10-12],... 

Huang, J.-M., Yokoyama, R., Yang, C.-S., and Fukuyama, Y. (2000) Merilactone A, a novel neurotrophic sesquiterpene dilactone from lllicium merrillianum. Tetrahedron Letters, 41, 6111-6114. 

During the total synthesis of the pentacyclic sesquiterpene dilactone (+)-merrilactone A by S.J. Danishefsky et al., a two-carbon unit was introduced at C9 by a Johnson-Claisen rearrangement. This high yielding transformation was carried out in the presence of catalytic 2,2-dimethyl propanoic acid at 135 °C using mesitylene as the solvent. A mixture of diastereomeric esters were formed, which were later hydrolyzed and subjected to iodolactonization to form the second lactone ring present in merrilactone A. The natural product was synthesized in 20 steps with an overall yield of 10.7%. 

S.J. Danishefsky and co-workers reported the total synthesis of pentacyclic sesquiterpene dilactone, merrilactone A. ° In their approach, they utilized Keck s radical allylation method to achieve the required chain extension. This sidechain was later used to construct one of the cyclopentane rings of the natural product. 

Kupchan S M, Hemingway R J, Werner D, Karim A 1969 Vernolepin, a novel sesquiterpene dilactone tumor inhibitor from Vernonia hymenolepis A Rich. J Org Chem 34 3903 - 3908... 

SCHEME 13.4. An asymmetric Heck reaction in the total synthesis of the elemanolide sesquiterpene dilactone (- -)-vernoIepin 9. 

Huang J, Yokoyama R, Yang C, Fukuyama Y. Merrilac-tone A a novel neurotrophic sesquiterpene dilactone from Illicium merrillianum. Tetrahedron Lett. 2000 41 6111 114. 

So far, Dendrobium species have yielded 21 pseudoalkaloids of the picrotoxane type and 27 sesquiterpene picrotoxanes (5 dilactones, 20 monolactones. 

Structural studies of sesquiterpene lactones have proven useful for understanding systematics and evolution in the genus Ambrosia (Asteraceae). Populations of Ambrosia psi-lostachya from the coastal islands off Texas produce only the dilactone compounds psilostachyin (90), psilostachyin B... 

Populations of Ambrosia confertifloray a ragweed disttib-uted widely through Texas and Mexico, reveal complex sesquiterpene lactone chemistry. Most populations from south-central Texas are characterized by a chromosome number n = 66 and the pseudoguaianolides confertiflorin (95) and desacetylconfertiflorin (99), whereas plants from northeastern Mexico yield germacranolides and a few eudesmanol-ides. All of those studied have chromosome number n = 54. A dilactone race (with both = 54 and n = 66) occurs further west in Texas and in Mexico along the western slopes of the Sierra Madre into the area where Ambrosia cumanensis occurs. A fourth race characterized by the presence of germacranolides occurs in northwestern Mexico (Mabry, 1972). 

The Diels-Alder adduct (389), on sequential hydrolysis, bromolactonization, and reductive debromination, was converted into the hydroxy-lactone (390), which, on Collins oxidation to (391) and Baeyer-Villiger ring-expansion, afforded the novel dilactone (392). Free-radical cyclization of the bromo-ketone (393), initiated by tri-n-butyltin hydride, gave a 3 2 mixture of the endo- and exo-derivatives (394), which, on separation and homologation, were transformed into the tricyclic sesquiterpenes sativene, endo-(395), and copacamphene, exo-(395). The use of bicyclo-... 

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