Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Ophiobolanes

Overall, however, the immensity of temperate land corresponds to a most various secondary metabolic production, different from that of tropical land. The most renowned alkaloids belong to the morphine class (Chart 6.2.A1), and, in combination with isoprenoids, to the ergot and triterpene classes (Chart 6.2. A2). Prominent in the peptides are the cyclosporins (the first of which was isolated from a fiingus collected in Norway), streptogramins, and P-lactams (Chart 6.2.P). The isoprenoids are represented by pyrethrin monoterpenes, cedrane sesquiterpenes, ginkgolide and taxane diterpenes, ophiobolane sesterterpenes, and arborane and amyrin-like triterpenes (Chart 6.2.1). In the polyketides, epothilones, recently discovered from Myxobacteria, and the long known rapamycin, are two prominent classes of macrolides (Chart 6.2.FA/PO/C). [Pg.27]

Valuable applications of this principle have been described by Paquette for the synthesis of topologically spheric molecules. Coates used this reductive fragmentation for the synthesis of bicy-clo[6.3.0]undecenecarboxylates, compounds which bear a structural resemblance to the a-b rings of the fusicoccin and ophiobolane natural products. Reduction of the unsaturated keto ester (164) affords an isomeric mixture of esters, the equilibration of which effects conversion to the single ester (165 Scheme 56). [Pg.1063]

Two new metabolites, 2-hexylidene-3-methylsuccinic acid 4-methyl ester 308 and an ophiobolane sesterterpene named halorosellinic acid 309, were... [Pg.275]

The intramolecular (4n + 4ti) photoaddition of furan-pyran-2-one bichromo-phores [e.g. (38) to give (39)] is potentially useful as an approach towards the fusicoccane/ophiobolane skeleton (Chase et al.), and the formation of (40) from the irradiation of (41) constitutes the first example of a (47t + 4ji) photocycloaddition of an enone to the benzene ring (Kishikawa et al.). Wender et al. continue to report elegant new applications of the intramolecular meta photocycloaddition of 5-phenylpent-l-ene derivatives and have described the synthesis of cis,cis,cis, traMi-[5,5,5,5]-fenestrane (42) using the photoreaction of (43) as a key step. Park... [Pg.8]

Halorosellinic acid (165) possessing an ophiobolane skeleton was isolated from the cultural broth of the marine fungus Halorosellinia oceanica. Compound 165 showed moderate antimalarial activity with IC50 value 13 pg/ml and weak antimycobacterial activity with MIC 200 pg/ml [170],... [Pg.145]

Halorsellinic acid (66) [Fig. (26)] is an ophiobolane sesterterpene isolated from the marine fungus Halorsellinia oceanica that showed in vitro antimalarial activity with IC50 = 13 pg/mL [85]. [Pg.198]

Ophiobolins. Phytotoxic sesterterpenoids derived from the unusual tricyclic skeleton of ophiobolane (C25H46, Mr 346.62). The O. A-M are produced by plant-pathogenic fungi such as Ophiobolus, Helmin-thosporium, Cephalosporium, and Drechslera species as well as by Aspergillus ustus (O. H and O. K), O. M is a potent nematocidal agent. [Pg.452]

Although fusicoccin is a C-25 compound, GGPP (1) is first converted to a cyclic diterpene and then modified to produce fusicoccin (West, 1981). This compound is similar in some regards to the ophiobolanes (see the section Sesterterpenes, below) (Stoessl, 1981). [Pg.415]

Sesterterpenes, C25 terpenoids, are relatively uncommon, primarily fungal metabolites, although some compounds of this series are known from higher plants and others from insect protective waxes (Cordell, 1974 Crews and Naylor, 1985 Hanson, 1972). The principal type of sesterterpenes includes the fungal metabolites known as ophiobolanes. Two... [Pg.420]

Ophiobolanes sesterterpene phytotoxins present in various species of Helminthosporum and Cochlio-bolus. Ophiobolin A (ophiobolin, cochliobobin, co-chliobobin A) is thought to be responsible for some of the symptoms of com blight caused by Helminlhospor-... [Pg.472]

Phytotoxin a compound produced by a fungal or bacterial plant parasite, which is toxic to the plant. The term should not be confused with Plant toxin (see). Compared with the large number of plant parasites with demonstrable phytotoxic activity, ordy relatively few phytotoxins have been identified. See separate entries Altemaria altemata toxins, Coronatine, Fusicoccin, Gibberellins, Ophiobolanes Stemphylo-toxins, Tabtoxins... [Pg.521]

Sasterterpenes terpenes formed from five isoprene units (CjsHjo). They have a tricyclic skeleton, and have been isolated from insect secretions and lower fungi. See Ophiobolanes. [Pg.626]

Rigby et al. employed the Ireland-Claisen rearrangement in an approacdi to the ophiobolane ceroplasteric acid (Scheme4.118) [114]. The product was isolated as a 4 1 mixture of diastereomers at C2 (pentenoic acid numbering). The major product is consistent with rearrangement occurring via a chair transition state for an -silyl ketene acetal or a boat transition state for a Z-sUyl ketene acetal. [Pg.186]

The intramolecular photo [4-1-4]-cycloaddition of a pendant furan to a 2-pyrone has been applied to the development of a route leading to 5-8-5-tricyclic cyclooctanoid natural products. For example, irradiation of 2-pyrone 79 affords two kinds of [4-1-4]-cycloadducts 80, 81, whose structure is a skeleton of fusicoccane and ophiobolane (Scheme 29). ... [Pg.1676]

Three sesterterpenes (624, 625, 626) have been isolated from the genus Cheilanthes (357, 358, 359). Cheilarinosin (624) has the same ophiobolane skeletone as the ophiobolins, which are phytotoxins produced by plant pathogens, Helminthosporium (360) and Cochliobo-lus (361). [Pg.71]


See other pages where Ophiobolanes is mentioned: [Pg.313]    [Pg.31]    [Pg.158]    [Pg.456]    [Pg.457]    [Pg.1029]    [Pg.313]    [Pg.244]    [Pg.174]    [Pg.1029]    [Pg.4]    [Pg.97]    [Pg.1019]    [Pg.103]    [Pg.84]    [Pg.472]    [Pg.472]    [Pg.493]    [Pg.83]    [Pg.174]   
See also in sourсe #XX -- [ Pg.84 ]

See also in sourсe #XX -- [ Pg.415 , Pg.422 ]




SEARCH



Ophiobolane

Ophiobolane synthesis

Ophiobolane via divinylcyclobutane rearrangement

© 2024 chempedia.info