Guaianolides from the Aerial Parts of Centaurea Hololeuca

Seven guaianolides were isolated from the acetone extract of the aerial parts of Centaurea hololeuca Boiss. The antifeedant activity of the natural compounds (1–7) and of four chloro derivatives (8–11), synthesized from repin (1) and janerin (3) were tested against larvae of Spodoptera littoralis. Cebellin J (6) and chlorojanerin (11) showed significant antifeedant activity at 100 ppm, whereas at this concentration cebellin G (4) and 15-deschloro-15-hydroxychlorojanerin (7) stimulated feeding. Cebellin G (4) stimulated larvae of S. littoralis to feed at low concentration, but deterred feeding at high concentrations. The addition of chlorine to repin (1) resulted in an increase in antifeeda…

Acid-induced rearrangement of epoxygermacra-8,12-olides: synthesis and absolute configuration of guaiane and eudesmane derivatives from artemisiifolin

A study on the acid-induced rearrangement of 4,5-epoxy- and 1,10-epoxygermacra-8,12-olides was carried out. From a 4,5-epoxy derivative, guaianes were obtained, whereas 1,10-epoxy derivatives furnished, depending on the stereochemistry of the C-1/C-10 epoxy ring, trans-5β,10α- or trans-5α,10β-eudesmanolides.

1,2,4-Ossadiazoli come “nitrogen-donor” nella sintesi foto-indotta di aziridine

Guaianolides and lignans from the aerial parts of Centaurea ptosimopappa.

The genus Centaurea L. (Asteraceae, tribe Cardueae, subtribe Centaureinae) comprises ca. 600 species distributed in Asia, Europa, North Africa and America (Hickey and King, 1981; Heywood, 1979). Turkish flora numbers 187 species, 114 of which being endemic (Davis, 1975; Davis et al., 1988; Wagenitz et al., 1988; Guner et al., 2000; Duran and Duman, 2000; Turkoglu et al., 2003). Centaurea ptosimopappa Hayek is an endemic species distributed in the Mediterranean and South-Eastern Anatolian regions of Turkey; widespread and locally frequent in the Amanos and Casus mountains (Davis, 1975; Reeves and Adiguzel, 2004). Aerial parts of C. ptosimopappa were collected in Hatay, the Amanos Mountain ab…

Cytotoxic activity of some natural and syntetic sesquiterpene lactones

Several natural and synthetic sesquiterpene lactones with different skeletons were tested and found to be active against nine cancer cell lines. Elemane (4), heliangolane (5) and their hydroxy analogues 9 and 10, all containing an α,β-unsaturated aldehyde substituent, were the most potent compounds.

Sintesi di lattoni sesquiterpenici e loro attività citotossica

Cytotoxic geranylflavonoids from Bonannia graeca

The analysis of the aerial parts of Bonannia graeca led to the isolation and characterization of two new polar geranylated flavonoids (6 and 7). The structure elucidation was performed by extensive spectroscopic methods (1D and 2D NMR) and comparison with literature data. All natural flavonoids isolated from B. graeca (1–7) and some synthetic derivatives (8–11) were tested for cytotoxic activity against four human tumor cell lines. Preliminary structure-activity relationship correlations are discussed.

The cytotoxic activity of natural and semisynthetic sesquiterpene lactones

Guaianolides from Centaurea babylonica

The cytotoxic activity of natural and semisynthetic guaianolides

Lignans and an unusual steroids from the seeds of Centaurea sclerolepis Boiss

Cytotoxic activity of some natural and synthetic guaianolides

Several natural guaianolides and synthetic derivatives of repin (1) were tested and found to be active against tumor cell replication. Repin (1) and both mono- and di-halohydrin analogues (2, 7-9, 11, 12) showed significant antitumor potency. A more effective compound (17) was obtained by esterificating repin with the paclitaxel side chain.

Rearrangement of Germacranolides. Synthesis and Absolute Configuration of Elemane and Heliangolane Derivatives from Cnicin

A study of the Cope rearrangement of 15-oxo-germacranolides to 15-oxo-elemanolides has been carried out. The synthesis of two natural elemanolides, isolated from Centaurea paui, and an efficent isomerization of the C-4/C-5 double bond of 15-oxo-germacranolides to form heliangolides are reported. The absolute configuration of all the compounds has been ascertained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Hastifolins A-G, antefeedant neo-clerodane diterpenoids from Scutellaria hastifolia

From the aerial parts of Scutellaria hastifolia, family Lamiaceae (Labiatae), seven neo-clerodane diterpenoids (hastifolins A-G) were isolated. The products are similar to the known scuteparvin and are characterized by being trans-cinnamoyl derivatives. Structures and stereochemistry were determined by intensive NMR investigation. Six of the products form three pairs of epimers at C-13. Hastifolins A-C showed significant antifeedant activity.

Biological activities of natural guaianolides from Centaurea hololeuca Boiss and their derivatives

Acid Rearrangment of Epoxy-germacranolides and Absolute Configuration of 1β,10α-Epoxy-salonitenolide

The acid-catalyzed cyclization of mono epoxides of cnicin acetonide (3) was investigated. Several 6,12-eudesmanolides were obtained, and their stereochemistry established by extensive spectroscopic analyses. Chemical correlations also led to the assignment of the absolute configuration of 1β,10α-epoxy-salonitenolide (13), a previously isolated natural product. The cytotoxic activities of some compounds were determined against A549 and MCF-7 tumor cell lines. The esterified germacranolides 2–6 were selectively cytotoxic against the MCF-7 breast cancer cell line.

Essential oil from the aerial parts of Centaurea cuneifolia Sibth. & Sm. and C. euxina Velen., two species growing wild in Bulgaria

Abstract The volatile constituents of the aerial parts of Centaurea cuneifolia Sibth. & Sm. and Centaurea euxina Velen. from Bulgaria were extracted by hydrodistillation and were analyzed. The main components in C. cuneifolia were β-eudesmol (26.5%) and hexadecanoic acid (17.6%). The main components in C. euxina were hexadecanoic acid (20.3%), spathulenol (10.8%) and caryophyllene oxide (6.2%). The chemotaxonomic significances with respect to other previously studied species of the same sections ( Achrolopus and Phalolepis , respectively) are discussed.

Sesquiterpene lactones from Anthemis wiedemanniana

Asteraceae; Anthemis wiedemanniana; sesquiterpene lactones; germacranolides; eudesmanolide

On the photoreaction of some 1,2,4-oxadiazoles in the presence of2,3-dimethyl-2-butene. Synthesis of N-imidoyl-aziridines

Fhe photochemistry of some 3,5-disubstituted 1,2,4-oxadiazoles in the presence of 2,3-dimethyl-2-butene has been investigated. The irradiation in acetonitrile yielded differently substituted N-imidoyl-aziridines through an aziridination reaction involving an acyliminonitrene intermediate. Pyrolysis of N-imidoyl-aziridines produced the corresponding N-allylamidines through a ring opening process.