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PubMed1997

Novel Syntheses of alpha,beta-Unsaturated Esters, alpha,beta-Unsaturated gamma-Lactones, and 2-Alkoxypyrroles via 1,2,4-Triazole-Stabilized Allenic Anions.

The dianion 12 (right harpoon over left harpoon 13) of 1-(1,2,4-triazol-1-yl)phenylpropargyl ethyl ether 11(readily prepared from phenylpropargylaldehyde diethyl acetal 8 and 1,2,4-triazole) reacts with alkyl halides, aldehydes, ketones, and alpha,beta-unsaturated ketones to give exclusively gamma-substituted allenic products of type 10. These adducts underwent mild in situ hydrolysis enabling convenient syntheses of alpha,beta-unsaturated esters 9a-c and alpha,beta-unsaturated gamma-lactones 16, 18, 20, and 22. Reactions of dianion 13 with imines generated the 1,3,4-trisubstituted 2-alkoxypyrroles 27, 30, and 31 in high yields. The alkyl-substituted analog 34 underwent similar reactions to give predominantly the gamma-products 39,40, and 42 along with a small proportion of alpha-analogs.

Journal Article↗
PubMed1997

Synthesis of XylbetaCer, Galbeta1-4XylbetaCer, NeuAcalpha2-3Galbeta1-4XylbetaCer and the Corresponding Lactone and Lactam Trisaccharides.

2-(Trimethylsilyl)ethyl 2-O-benzoyl- and 2,3-di-O-acetyl-beta-D-xylopyranosides (12 and 14) were synthesized in high yields and subjected to glycosylation with various glycosyl donors. Galactosylation of 12 gave the xylose analogue of TMSEt lactoside (3), which was transformed into the glycosyl acceptor 19. Sialylation then gave the xylose analogue of G(M3) trisaccharide (5). The TMSEt glycosides 10, 25, and 32 were transformed into the corresponding trichloroacetimidates, which were used for glycosylation of an azidosphingosine derivative. The resulting sphingosyl glycosides were transformed into the title ceramides. Treatment of NeuAcalpha2-3Galbeta1-4XylbetaCer (5) with acetic acid gave the corresponding 1"-->2'-lactone 7. Glycosylation of 12 or 14 with a G(M4)-lactam donor (40) gave the xylose analogue of G(M3)-lactam (42). There was a 3-fold increase in the formation of GAG chains in the presence of 0.5 &mgr;M XylbetaCer (2) in the medium.

Journal Article↗
PubMed1997

Titanocene-Catalyzed Reduction of Lactones to Lactols.

A convenient method for the conversion of lactones to lactols is described. The hydrosilylation to lactols is carried out via air-stable titanocene difluoride or a titanocene diphenoxide precatalyst using inexpensive polymethylhydrosiloxane (PMHS) as the stoichiometric reductant. These procedures have been demonstrated with a variety of substrates and proceed in good to excellent yield.

Journal Article↗
PubMed1999

An Approach toward the Triquinane-Type Skeleton via Reagent-Controlled Skeletal Rearrangements. A Facile Method for Protection-Deprotection of Organomercurials, Tuning the Selectivity of Wagner-Meerwein Migrations, and a New Route to Annulated Lactones.

Nonlinear triquinane-type building blocks have been synthesized using three strategic steps, namely, (1) Hg(2+)-mediated opening of a cyclopropane ring involving a skeletal rearrangement (3 --> 8), (2) an intramolecular organometallic addition across a C=O bond triggered by activation of the C-HgX group by means of Me(3)CuLi(2) (14 --> 26), and (3) selective, reagent-controlled skeletal rearrangements (43 --> 47 with Tl(3+) or Hg(2+); 43 --> 51 + 52 with Pd(2+); 44 --> 47 with Pd(2+)). A new method for protection/deprotection of organomercurials has been developed, which allows selective reduction of a carbonyl group with NaBH(4) and other hydrides (8 --> 14 --> 16 --> 20) and Tebbe methylenation (14 --> 31 --> 32). Oxidative demercuration (8 --> 11 + 28) and Pd(2+)-catalyzed carbonylation of organomercurials (20 --> 53) allowed syntheses of gamma- and delta-lactones.

Journal Article↗
PubMed2001

Furodysin lactone and pyrodysinoic acid, new sesquiterpenes from a Philippines Dysidea species.

Chemical investigation of a Dysidea sponge, collected at Siquijor, Philippines, has afforded two new sesquiterpenoid metabolites, which we have termed furodysin lactone (1) and pyrodysinoic acid (2). The known 3,6,11-trihydroxy-9,11-secoergostane-7,24(28)-dien-9-one (3) was also encountered. Structure elucidation of the isolated metabolites involved high-field 2-D NMR spectroscopy including (1)H-(1)H COSY, HSQC, and HMBC.

Animals↗
PubMed2005

Lajollamycin, a nitro-tetraene spiro-beta-lactone-gamma-lactam antibiotic from the marine actinomycete Streptomyces nodosus.

A strain of Streptomyces nodosus (NPS007994) isolated from a marine sediment collected in Scripps Canyon, La Jolla, California, was found to produce lajollamycin (1), a nitro-tetraene spiro-beta-lactone-gamma-lactam antibiotic. The structure was established by complete analysis of spectroscopic data and comparison with known antibiotics oxazolomycin (2), 16-methyloxazolomycin (3), and triedimycin B (4). Lajollamycin (1) showed antimicrobial activity against both drug-sensitive and -resistant Gram-positive bacteria and inhibited the growth of B16-F10 tumor cells in vitro.

Animals↗
PubMed2006

Awajanomycin, a Cytotoxic gamma-lactone-delta-lactam metabolite from marine-derived Acremonium sp. AWA16-1.

The new fungal metabolite awajanomycin (1), which has gamma-lactone-delta-lactam rings, was isolated from the marine-derived fungus Acremonium sp. AWA16-1, which had been collected from sea mud off Awajishima Island in Japan. The structure of 1 was elucidated by spectroscopic analysis and chemical methods. Awajanomycin (1) and its derivative (2) inhibited the growth of A549 cells with IC(50) values of 27.5 and 46.4 microg/mL, respectively.

Acremonium↗
PubMed2006

Crassolides A-F, cembranoids with a trans-fused lactone from the soft coral Sarcophyton crassocaule.

Six new polyoxygenated cembrane-based diterpenoids possessing a trans-fused alpha-methylene-gamma-lactone, crassocolides A-F (1-6), have been isolated along with the known compound 7 from the ethyl acetate extract of a Taiwanese soft coral, Sarcophyton crassocaule. The structures of 1-6 have been established by detailed spectroscopic analysis, including 2D NMR (1H-1H COSY, HMQC, HMBC, and NOESY) spectroscopy, while their absolute configurations were determined using a modified Mosher's method for 1. The structure of 5 was further proven by X-ray diffraction analysis. The full assignment of NMR data of 7 is reported herein for the first time. The cytotoxicity of crassocolides 1-4, 6, and 7 against a limited panel of cancer cells was also determined.

Animals↗
PubMedDate not supplied

Mode of action of the sesquiterpene lactone, tenulin, from Helenium amarum against herbivorous insects.

Tenulin [1], a sesquiterpene lactone from Helenuim amarum, is a potent antifeedant to the European corn borer Ostrinia nubilalis. At 3 mumol/g in artificial diets, 1 reduced growth and delayed larval development of O. nubilalis and the variegated cutworm Peridroma saucia larvae. An especially pronouned carry-over effect in O. nubilis was substantial reduction in fecundity of adult moths resulting from treated larvae. The LD50 (lethal dose for 50% mortality) of 1 by injection in the migratory grasshopper Melanoplus sanguinipes was 0.88 mumol/insect. Toxicity in M. sanguinipes was antagonized by co-administration of cysteine, suggesting that the cyclopentenone group of tenulin undergoes Michael addition of biological nucleophiles in vivo. This mechanism was partially confirmed by the finding that only tenulin analogues capable of acting as electrophic acceptors had significant antifeedant activity.

Animals↗
PubMedDate not supplied

New cytotoxic lupane lactones from Kokoona ochracea.

Three new compounds, ochraceolides A, B, and C, were isolated from nonpolar extracts derived from Kokoona ochracea stem bark. Based on spectroscopic data, their structures were determined to be the closely related lupane lactones: 3-oxolup-20(29)-en-30,21 alpha-olide, 20,29-epoxy-3-oxolupan-30,21 alpha-olide, and 3,6-dioxolup-20(29)-en-30,21 alpha-olide. Compounds 1 and 3 exhibited significant cytotoxic activity with cultured P-388 cells (ED50 values of 0.26 and 0.53 microgram/ml, respectively) but were at least tenfold less active with a variety of human tumor cell lines. Compound 2 was weakly active with cultured P-388 and KB-3 cells (ED50 values of 7.8 and 5.2 micrograms/ml, respectively), but no significant activity was observed with other human cancer cell types (ED50 values of more than 20 micrograms/ml).

Animals↗
PubMed1993

Further lupane lactones from Kokoona ochracea.

Additional new lupane lactones were isolated from the stem bark of Kokoona ochracea (Celastraceae). Their structures have been elucidated, through the application of 1D and 2D nmr spectroscopic methods, as 20,29-dihydroxy-3-oxolupan-30,21 alpha-olide (ochraceolide D) [1] and 28-hydroxy-3-oxolup-20(29)-en-30,21 alpha-olide (ochraceolide E) [2]. These compounds and the mono- and di-acetates of ochraceolide D (4 and 5, respectively) were evaluated for in vitro cytotoxic activity against P-388 murine lymphocytic leukemia cells and a panel of human cancer cell systems. Ochraceolide D [1] was significantly cytotoxic (ED50, 3.9 micrograms/ml) against human glioblastoma (U373) cells. Other compounds (4, 5, and 2) exhibited only a weak cytotoxic response in certain cancer cell lines.

Animals↗
PubMed1998

New Sesquiterpene Lactones and Other Constituents from Helianthuspetiolaris

Three new sesquiterpene lactones, 11alpha,13-dihydroxydehidrocostuslactone (1), the unusual 5, 10-epoxygermacranolide 4,15-anhydrohelivypolide (2), and 3-methoxy-1,2-anhydridoniveusin A (4), together with the 5,10-epoxygermacranolide helivypolide, four known 3,10-furanoheliangolides, and five known kaurane- and trachylobane-type diterpenes, have been isolated from Helianthus petiolaris.

Journal Article↗
PubMed1998

Gloeolactone, a New Epoxy Lactone from a Blue-Green Alga

A novel lactone, gloeolactone (1), has been isolated from the blue-green alga, Gloeotrichia sp. The structure of this compound has been elucidated from a detailed analysis of the NMR spectra. This compound was shown to be toxic to brine shrimp.

Journal Article↗
PubMed1999

Microbial transformation of sesquiterpene lactones by the fungi cunninghamella echinulata and rhizopus oryzae

Incubations of the fungi Cunninghamella echinulata and Rhizopus oryzae with the sesquiterpene lactones (+)-costunolide (1), (+)-cnicin (2), (+)-salonitenolide (3), (-)-dehydrocostuslactone (4), (-)-lychnopholide (5), and (-)-eremantholide C (6) were perfomed. Incubation of 1 with C. echinulata afforded Delta11(13)-dihydrogenation and Delta1(10)-epoxidation products (7-10). C. echinulata also hydrolyzed the side chain of 2, and transformed 4 into (+)-11alpha,13-dihydrodehydrocostuslactone (12), a new natural product. R. oryzae converted 4 into both Delta11(13)-dihydrogenation and Delta10(14)-epoxidation products (16 and 17). Both fungi transformed 5 into (-)-16-(1-methyl-1-propenyl)eremantholanolide (13), providing experimental evidence for the biosynthesis of the eremantholide hemiketal unit. Compounds 3 and 6 were not metabolized by either fungus under the test conditions.

Journal Article↗
PubMed1999

Sesquiterpene lactones from neurolaena oaxacana

Twelve sesquiterpene lactones, two new (1 and 2) and 10 known neurolenin-type germacranolides and furanoheliangolides (3-12) were isolated from Neurolaena oaxacana, and their structures were elucidated by NMR and GC-MS analysis. The chemotaxonomic importance of these findings is discussed. As N. lobata is used against dysenteries, neurolenin B (4) and a mixture of the neurolenins C (5) and D (6) were tested against Entamoeba histolytica and Giardia intestinalis.

Journal Article↗