Aurea Perales

Asteriscanolide: a sesquiterpene lactone with a new natural skeleton

Abstract A sesquiterpene lactone was isolated from the hexane extract of Asteriscus aquaticus . Its constitution and stereochemistry were determined by spectroscopic techniques, principally two-dimensional NMR correlations (COSY, HCCORR, RELAY) and with the interpretation of certain chemical transformations. The results were confirmed by X-ray diffraction and the name asteriscane is proposed for the new natural skeleton.

Scutalpin a, a neo-clerodane diterpene from scutellaria alpina

Abstract A new neo -clerodane diterpenoid, scutalpin A, has been isolated from Scutellaria alpina . The structure of scutalpin A [7 β ,19-diacetoxy-6 α -(2′ S )-methylbutyryloxy-4 α ,18; 8 β ,13 S -diepoxy- neo -clerodan-15,16-olide] was established by spectroscopic methods, including an X-ray diffraction analysis which provided its absolute stereochemistry.

Intermediates with biosynthetic implications in de novo production of phenyl-phenalenone-type phytoalexins by Musa acuminata. Revised structure of emenolone

Abstract Three new intermediates ( 1 – 3 ) in de novo biosynthetic pathway to phenyl-phenalenone-type phytoalexins have been isolated from rhizomes of Musa acuminata infected with the fungus Fusarium oxysporum . The structures of the new pre-phytoalexins were elucidated on the basis of spectroscopic evidences, chemical correlation and acid catalyzed biomimetic cyclization of 1 to emenolone ( 4 ), isolated from the same source and whose previously reported structure has been unambiguously corrected by X-ray diffraction analysis. The chemical shift for all of the hydrogen and carbon atoms in the substances were unambiguously established by mono- and bidimensional, homo- and heteronuclear NMR experiments ( 1 H NMR, 1 3C NMR, COSY, ROESY, HMQC and HMBC).

A chlorine-containing and two 17β-neo-clerodane diterpenoids from teucrium polium subsp. Vincentinum

Abstract From the aerial parts of Teucrium polium subsp. vincentinum three new neo-clerodane diterpenoids, teuvincentins A, B and C, have been isolated besides four already known diterpenes (19-acetylgnaphalin, eriocephalin, isoeriocephalin and 3-deacetyl-20- epi -teulanigin) and the flavones cirsiliol and apigenin. The structures of teuvincentin A [(12 S , 20 S )-20- O -acetyl-19-acetoxy-18-chloro-15,16-epoxy-4α,7-dihydroxy-6-oxo- neo -clerodane-7,13(16),14-triene-20,12-hemiacetal], B [12 S ,20 S )-20- O -acetyl-4α,18;15,16-diepoxy-6α-hydroxy-17β- neo -clerodane-13(16),14-diene-7α,19; 20,12-dihemiacetal] and C [12 S ,20 S )-20- O -acetyl-6α,19-diacetoxy-4α,18; 15,16-diepoxy-7-oxo-17β- neo -clerodane-13(16), 14-diene-20,12-hemiacetal] were established by chemical and spectroscopic means and, in the case of teuvincentins A and B, also confirmed by X-ray diffraction analyses of their acetyl derivatives.

Structure and absolute configurations of Dictyota sp. diterpenes

Eight diterpenes belonging to the dolostane carbon skeleton have been isolated from the Canary Island brown alga Dictyola sp. The structures including absolute configuration of these diterpenes were secured by X-ray analysis of the triol derivative 7 followed by chemical interconversions.

Mulinic and isomulinic acids. rearranged diterpenes with a new carbon skeleton from Mulinum crassifolium

Abstract Two new diterpenoids, mulinic and isomulinic acids, have been isolated from the aerial parts of Mulinum crassifolium (Umbelliferae). The structure of mulinic actd (1) was determined by a combination of spectroscopic and single-crystal X-ray diffraction analyses.The proposed structure of isomulinic acid (2) was based on spectroscopic comparison with mulinic acid and on chemical grounds. The diterpenoids 1 and 2 possess a novel carbon skeleton whose plausible biogenetic pathway from a suitable labdane derivative is briefly discussed.

New Phenalenone-type Phytoalexins from Musa acuminata (Colla AAA) Grand Nain

Abstract Four new phenalenone-type phytoalexins (2–5) have been isolated from rhizomes of Musa acuminata (AAA) infected with the fungus Fusarium oxysporum. The structures of the new phytoalexins were elucidated using spectroscopic evidence, chemical correlation, synthesis, and X-ray diffraction analysis. The major compound 2, has been previously described as a natural product, named anigorufone, but never as a phytoalexia. The chemical shift for all of the hydrogen and carbon atoms in the substances were unambiguously established by mono- and bidimensional, homo- and heteronuclear NMR experiments (1HNMR, 13CNMR, COSY, HMQC and HMBC). In preliminary in vitro assays, all of the four new phytoalexins have shown inhibitory activity on the growth of the germinative tube of Fusarium oxysporum f. sp. cubense race 4.

Reactions of Ru(CO)Cl(RCCHR′)(PPh3)2 with carboxylates. The crystal structure of Ru(O2CMe)(CO)(HCCHPh)(PPh3)2

Abstract The 16-electron complexes Ru(CO)Cl(RCCHR′)(PPh 3 ) 2 (R = H, R′ = CMe 3 , SiMe 3 , Ph, CO 2 Me and CO 2 Et; R = R′ = H, Me, Ph and CO 2 Me react readily with carboxylates to give the saturated complexes Ru(O 2 CR″)(CO)(RCCHR′)(PPh 3 ) 2 (R″ = Me and Et). The crystal structure of the complex Ru(O 2 CMe)(CO)(HCCHPh)(PPh 3 ) 2 has been determined, and reveals an octahedral geometry for the ruthenium atom bearing two phosphines in a trans -disposition and η 2 -acetate, CO and η 1 -phenylethenyl ligands.

Rearranged abietane diterpenoids from the root of teucrium polium subsp. vincentinum

Abstract From the root of Teucrium polium subsp. vincentinum (Labiatae) four new rearranged abietane derivatives, teuvincenones A, B, C, and D (1-4, respectively), have been isolated. Two of these compounds, teuvincenones C (3) and D (4), possess a novel hydrocarbon skeleton which contains a cyclopropane ring constituted by the C-3, C-4, and C-18 carbons of the 17(15→16)-abeo-abietane framework. The structures of these diterpenoids were established mainly by spectroscopic means and, in the case of teuvincenones A (1) and C (3), also confirmed by X-ray diffraction analyses.

Chemical ecology of canarian laurel forest: Toxic diterpenes fromPersea indica (Lauraceae).

The tree speciesP. indica (Lauraceae) is an important endemism in the Canary Islands laurel forest and can readily be distinguished by its defoliated appearance due to the seasonal action of wild rats (Rattus rattus), which eat the plant and become intoxicated. These observations and the phytochemical interest of this plant species led us to study the potentially toxic chemicals responsible for such action. We found that an ethanolic extract ofP. indica and its water fraction were toxic when injected into laboratory mice. The mice also died after ingestion of the stems and showed a significant preference for those extracted and rehydrated with an 8% aqueous extract solution when compared with the water control. Two compounds that have been isolated from the toxic fraction and identified by spectroscopic methods are the polyhydroxy pentacyclic diterpenes ryanodol and cinnceylanol. Possible ecological implications are discussed.