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(IPNA) Artículos post-print
Mostrando recursos 1 - 20 de 89
Microbial transformation of 18-hydroxy-9,13-epi-ent-pimara-7,15-diene by Gibberella fujikuroi - Fraga, Braulio M.; González, Pedro; Hernández, Melchor G.; Chamy, María C.; Garbarino, Juan A.
The incubation of the diterpene 18-dihydroxy-9,13-epi-ent-pimara-7,15-diene(3) with the fungus Gibberella fujikuroi gave 14 metabolites, 4 and 6-18. The carbons functionalized were the C-20 methyl and all the secondaries, except C-12. The main reaction observed was the epoxidation of the 7,8-double bond, which rearranged to form 7-keto derivatives, such as 10-17, or the allylic alcohol 18. Compound 9 was the only one obtained in which the 7,8-double bond of the substrate remained unaltered. This work confirms that, in the feeding of this type of diterpene with this fungus, the oxidation at C-19, typical of the biosynthesis of gibberellins from ent-kaur-16-ene. is...
Biotransformation of the diterpenes epicandicandiol and candicandiol by Mucor plumbeus - Fraga, Braulio M.; Alvarez, Alvaro; Suárez, Sergio
The microbiological transformation of the diterpene epicandicandiol (1) with Mucor plumbeus gave foliol (3), sideritinol (5), and 7$, 16$, 17, 18-tetrahydroxy-ent-kaurane (7), while the incubation of candicandiol (2) gave 7$,9$, 18-trihydroxy-ent-kaur-16-ene (10), canditriol (11), and 7$,16$, 17, 18-tetrahydroxy-ent-kaurane (12). Thus, the main difference observed in both feedings, resulting from the spatial change in the orientation of the 7-hydroxyl, from axial in the substrate 1 to equatorial in 2, was the formation of a 3$- and a 9$-hydroxylated derivative, respectively.
Insect antifeedant ryanodane diterpenes from Persea indica - González-Coloma, Azucena; Terrero, David; Perales, Áurea; Escoubas, Pierre; Fraga, Braulio M.
The new ryanodane diterpenes cinnzeylanone, ryanodol 14-monoacetate, and epi-cinnzeylanol have been isolated from Persea indica(Lauraceae). The structure of cinnzeylanone has been determined by X-ray analysis. These compounds proveds to be antifeedants against Spodoptera litura. Cinnzeylanol and ryanodol were the most active antifeedants of this plant, with a range of activity close to that of ryanodine. THis is the first report on the antifeedant effects of this class of diterpenes. Their structure-activity relationships and possible mode of action are discussed.
Iodosobenzene diacetate, an efficient reagent for the oxidative decarboxylation of carboxylic acids - Concepción, José I.; Francisco, Cosme G.; Freire, Raimundo; Hernández, Rosendo; Salazar, José A.; Suárez, Ernesto
The oxidative decarboxylation of organic acids with concomitant replacement by a halogen (halodecarboxylation), through a radical intermediate, in the Hunsdiecker or modified Hunsdiecker reaction comprises an extremely useful and selective procedure for the syntheses of halogenated organic substances. The oxidative elimination of the intermediate radicals to give olefins is an interesting variation of the decarboxylation reaction of acids, which is usually accomplished with lead tetraacetate
Synthesis of (+)-8-deoxyvernolepin - Hernández, Rosendo; Velázquez, Silvia M.; Suárez, Ernesto
A short and efficient synthesis of (+)-8-deoxyvernolepin (2) from (-)-α-santonin (8), by functionalization of the angular methyl from a 2β- or 6β-alkoxy radical generated by reaction of the alcohol 6 or 7 with diphenylhydroxyselenium acetate and iodine and l,4-fragmentation of the γ-hydroxystannane
35 using hypervalent organoiodine reagents as the key steps, is described. The most important structural features of this compound and other vernolepin congeners, the δ-valerolactone cis-fused to ring B moiety and the angular vinyl group, are introduced in the same step.
Structure and absolute configuration of spathulasin, a metabolite of Aeonium spathulatum - Hernández, Rosendo; Rivera, Augusto; Suárez, Ernesto; Prangé, Thierry
A new metabolite, spathulasin (l), is described as a natural product from Aeonium spathulatum. The structure of the 14-membered lactone derivative 10 was determined by X-ray crystallographic analysis. Hydrolysis of
spathulasin and identification of the pentose portion as L-arabinose allowed the assignation of the absolute configuration of all centers in 1.
One-step preparation of the 3,3'-dimer of precocene II - Fraga, Braulio M.; Pérez García, V.
The antijuvenile hormones precocenes I (1) and II (2) have been shown to induce precocious metamorphosis when applied to larval stages of insects. As a consequence of this effect several analogues of both compounds have been synthesized in a search for compounds with better activity. We have prepared several dimers, the most representative being dimers B (3) and C (4), which have been obtained by treatment of precocene II (2) with Lewis acids.
Consideraciones sobre la biosintesis de los nor-triterpenos de las Celastraceas - González, A. G.; Fraga, Braulio M.; Ravelo, Ángel G.; Luis, J. G.; Ferro, Esteban; González, Carmen M.; Bazzocchi, Isabel L.
Las Celastraceas se encuentran ampliamente distribuídas por todas las zonas tropicales y cálido-templadas del mundo'. Esta familia se encuentra representada en la Macaronesia por dos especies endémicas, el Maytenus canariensis (Loes) Kunk. et Sund (Catha cassinoides), que crece en todas las Islas Canarias excepto en la de Lanzarote, y el Maytenus driadndry (Lowe) Loes, que lo hace en las Islas de Madeira y Porto Santo.
Caractrísticas mineralógicas de la Fracción inferior a 2μ en dystrandepts (II) - Cabezas Viaño, O.; Rodríguez Pascual, C.; Fernández Caldas, E.; Hernández Moreno, J.
The mineralogical composition of the clay fraction (minus-two-micron) of three soils profiles, has been studied by X ray diffraction and I. R. absorption techniques. Allophane is the most abundant mineral. The kaolin group is represented, mainly by halloysite as accompanying mineral. Quart is present mainly in the more superficial soil horizons.
In the clay fraction of these soil profiles, primary minerals have sometimes be found (felpars, pyroxenes, hematites, etc,) but they use be present in a much lower proportion than in other andosols of the Canary Islands.
Características mineralógicas de la fracción inferior A 2$ en vitrandepts (IV) - Hernández Moreno, J.; Fernández Caldas, E.; Rodríguez Pascual, C.; Cabezas Viaño, O.
The mineralogical composition of the clay fraction ($2u) of four soil profiles from Zahagu, Tajanara, Chio. Chinyero, have been studied by X-ray diffraction and I. R. absorption techniques. This clay fraction contains a great amount of amorphous gels and some kaolin-type minerals (hallosyte and disordered kaolinite, probably in a transformation stage), they also contain allophane and illite.
Primary minerals present in the clay fraction of the four profiles are felspars and piroxenes.
Quartz and a-crystohallite are also founds in the clay fraction in some soil horizons.
Genotoxic activity of halogenated phenylglycine derivatives - Boto, Alicia; Gallardo, Juan Antonio; Hernández, Rosendo; Ledo, Francisco; Muñoz, Ana; Murguía Ibáñez, José Ramón; Menacho-Márquez, Mauricio; Orjales, Aurelio; Saavedra, Carlos J.
The discovery of genotoxic amino acids derived from phenylglycine, and posessing halogen substituents, is described. The utility of hypervalent iodine reagents in the synthesis of this class of compounds is highlighted. The mechanism of action of the (haloaryl)glycines was studied in Saccharomyces cerevisiae.
Synthesis of functionalized nitrogen heterocycles from β- and γ-amino acids by radical decarboxylation - Boto, Alicia; Hernández, Rosendo; León, Yolanda de; Murguía Ibáñez, José Ramón; Rodríguez-Afonso, Abigail
The radical decarboxylation of β- and γ-amino acids on treatment with PhI(OAc)2–I2 is a mild and efficient methodology to synthesize halogenated or oxygenated nitrogen heterocycles. The reaction was applied to the synthesis of bioactive products, such as opioid analogues, iminosugars and new antifungic agents.
Bacteria-enriched inoculant enhances banana development and influences nutrition - Fernández Falcón, Marino; Alvarez, Carlos Enrique; Borges-Pérez, Andrés; Borges Rodríguez, Andrés A.
The beneficial effects of bacteria in the soil are knwn, but those of commercial bacterial products, to enhance plant growth, remain unsolved. Therefore, the effect of RET-FLO PX357, a commercial mixture of microorganisms in a liquid suspension, was studied and quantitied on banana crop. Materials an methods. A concentrated culture of this product was tested for 2 years in two commercial banana plantations in Tenerife (Canary Islands, Spain). Three treatments were used: a control Fenemiphos nematicide (15 Laha$), and RET-FLO PX357 (20 Laha$). Parasitic root nematode number, pseudostem circunference, time to flowering, and bunch hand and finger number were determined;...
Determinaciones analíticas en suelos. Normalización de métodos (II. Potasio, Calcio y Magnesio - Abadía, Armando; Bara, S; Cadahia, C.; Casado, M.; Chaves, M.; Cruz, G.; Heras, L.; Lachica López, Manuel; Lasala, M.; Pérez, V.; Prat Pérez, L.; Romero, M.; Sánchez, B.
After our first paper about the determination of pH. organic matter and nitrogen appeared few years agc, our Group has followed working on the standardization of methods to be applied to the analytical determinations of soils. This second paper deals with the determination of extractable potassium, calcium and magnesium
A convenient and chemoselective one-pot oxidation/Wittig reaction for the C2-homologation of carbohydrate-derived glycols - Pinacho Crisóstomo, Fernando R.; Carrillo Fumero, Romen; Martín, Tomás; García-Tellado, Fernando; Martín, Víctor S.
A simple and convenient one-pot protocol for the chemoselective C2-homologation of carbohydrate-derived glycols is described. The method comprises the chemoselective oxidation of the glycol to the corresponding hydroxyaldehyde and the subsequent Wittig alkenylation. In addition, the method does not need selective protective group manipulation, and it is safe, economical, fast (5 to 6 h), and bench-friendly. Its general utility is discussed.
Synthesis and antiproliferative activity of (2R,3R)-disubstituted tetrahydropyrans. Part 2: Effect of side chain homologation - Carrillo Fumero, Romen; León, Leticia G.; Martín, Tomás; Martín, Víctor S.; Padrón, José M.
In this study, we synthesized a series of enantiomerically pure (2R,3R)- and (2R,3S)-disubstituted tetrahydropyrans bearing a CH2O spacer group on the side chain at position 2 of the heterocyclic ring. The in vitro antiproliferative activities of the compounds were examined in the human solid tumor cell lines A2780 (ovarian cancer), SW1573 (non-small cell lung cancer), and WiDr (colon cancer). Overall, the results point out the relevance for antiproliferative activity of the distance between the heterocycle and the unsaturated group.