Repositorio institucional del Consejo Superior de Investigaciones Científicas.
Digital.CSIC es un depósito de documentos digitales, cuyo objetivo es organizar, archivar, preservar y difundir en modo de acceso abierto la producción intelectual resultante de la actividad investigadora del CSIC.
(IPNA) Artículos post-print
Mostrando recursos 1 - 20 de 138
Nitroamine radicals as intermediates in the functionalization of non-activated carbon atoms - Hernández, Rosendo; Rivera, Augusto; Salazar, José A.; Suárez, Ernesto
Photolysis of N-iodonitroamines generated in situ from the steroidal nitroamines 6β-nitroamino-5α-cholestan-3β-ol acetate, 6β-nitroamino-5α-cholestane-3β,5α-diol diacetate, and 20R-nitroaminopregn-5-en-3-ol acetate removes hydrogen atoms from the Me-18 and Me-19 groups to give 6β-,19-N-nitroepinino-5α-cholestan-3β-ol acetate, 6β,19-N-nitroepinino-5α-cholestane-3β5α-diol diacetate, and 18,20R-N-nitroepiminopregn-5-en-3β-ol acetate.
Aminoselenenylation of alkenes: syntheses of β-phenylseleno carbamates and β-phenylseleno cyanamides - Francisco, Cosme G.; Hernández, Rosendo; León, Elisa I.; Salazar, José A.; Suárez, Ernesto
β-(Phenylseleno)alkylcarbamates and β-(phenylseleno)alkylcyanamides have been synthesized in good yields by reaction of alkenes with carbamates and cyanamide, respectively, in presence of benzeneselenenyl chloride–silver tetrafluoroborate or N-phenylselenophthalimide–H+. The subsequent reductive or oxidative removal of the phenylseleno group affords alkylcarbamates and alkylcyanamides, and allylic carbamates, cyanamides, and cyanimides.
Preparation of gibberellins A9 and A20 from gibberellic acid - Duri, Zvitendo J.; Fraga, Braulio M.; Hanson, James R.
Methyl gibberellate has been converted via the methyl ester of 3-epigibberellin A1 into the 3-chloro- and 3,13-dichloro-derivatives using triphenylphosphine and carbon tetrachloride. Hydrogenolysis of the chlorides with tributyltin hydride afforded gibberellins A20 and A9 as their methyl esters. Gibberellin A9 methyl ester was also prepared from the gibberellin A4/A7 mixture. The stereochemistry of the conjugate reduction of the ring-A-unsaturated ketone is defined.
The reaction of enols with superoxide anion radicals: preparation of tertiary α-ketols - Betancor, Carmen; Francisco, Cosme G.; Freire, Raimundo; Suárez, Ernesto
Pregnan-20-ones (1) and (4), and 3β-hydroxy-5α-cholestan-6-one (7) react with KO2 and 18-crown-6 in benzene solution and under an oxygen atmosphere at 6–7 °C to give the corresponding α-hydroperoxides (2), (5) and (8) which after treatment with Ph3P gives α-ketols (3), (6) and (9) in good yields.
Partial synthesis of a trachylobagibberellin analogue - Arráez, Jacinto D.; Fraga, Braulio M.; González, Antonio G.; Gutiérrez Luis, Javier; Fayos, José; Perales, Áurea
We have synthesized a trachylobagibberellin analogue (14) by rearranging a chloro-enol lactone obtained from trachinodiol (2). Its structure was determined by X-ray analysis. This implies that the stereochemistry previously given to a similar compound (20) obtained from epicandicandiol (19) by the same procedure, should be amended to (21).
Transannular participation of some C-19 esters in reactions at C-20 of gibberellin A13 - Fraga, Braulio M.; González, Antonio G.; Hernández, Melchor G.; García-Tellado, Fernando; Hanson, James R.; Hitchcock, Peter B.
Methanolysis or sodium borohydride reduction of the 3-acetoxy-7,19-dimethyl ester of gibberellin A13 20-toluene-p-sulphonyl anhydride afforded, respectively, the unusual 19-orthoester or epimeric 19-acetals as the major products rather than the products of simple displacement of the 20-toluene-p-sulphonoxy-group. The structure of the 19-orthoester was proven by X-ray analysis.
Partial synthesis of 4-epi-trachylobagibberellin A12 - Fraga, Braulio M.; Guillermo, Ricardo; Arráez, Jacinto D.; Gutiérrez Luis, Javier; Perales, Áurea
The partial synthesis of 4-epi-trachylobagibberellin A12, starting from the natural diterpene trachinodiol (ent-7 α,18-dihydroxytrachylobane) is reported. The stereospecific ring B contraction was carried out by treatment of a bromohydrin with silver oxide. The structure of a monoester of this gibberellin analogue was determined by X-ray analysis.
Ambiphilic allenes: synthesis and reactivity - Tejedor, David; Méndez-Abt, Gabriela; González-Platas, Javier; Ramírez, Miguel A.; García-Tellado, Fernando
Ambiphilic allenes are generated by an organocatalyzed domino reaction of alkyl propiolates and aromatic 1,2-diketones; in the absence of any external chemical agent, these allenes perform a thermally-driven dimerization reaction to generate the corresponding fully-substituted cyclobutanes in a regio- and highly stereoselective manner.
Induced resistance to Fusarium wilt of banana by exogenous applications of indoleacetic acid - Fernández Falcón, Marino; Borges, Andrés A.; Borges-Pérez, Andrés
Fusarium wilt of banana (Panama disease), caused by Fusarium oxysporum f.sp. cubense, is a soliborne systemic disease which occludes host vascular system. We report here two experiments on resistance induction with banana plants (cv. Dwarf Cavendish) carried out in glass greehouse with different indoleacetic acid treatments, which are capable of inducing resistance to Panama disease. The results obtained in these experiments suggest that the exogenous application of indoleacetic acid to banana plants induce resistance to Panama disease and that the resistance induction is more effective when performed using low doses and frequent applications. This work seems to confirm the role...
Tomato- Fusarium oxysporum interactions: II. Chitosan and MSB induced resistance against fol in young tomato plants - Paz-Lago, Dalila; Borges, Andrés A.; Gutiérrez, A.; Borges, Anna; Cabrera, G.; Ramírez, Miguel Angel; Falcón, A.
Qitosna, hidrolizados de quitosana y menadiona bisulfito de sodio (MBS), fueron aplicados al suelo y asperjados sobre plantas de tomate en diferentes experimentos, para evaluar su efecto combinado sobre el desarrollo de la enfermedad. Los tres productos protegieron con efectividad las plantas contra la enfermedad, mostrando los mejores resultados la aspersión al follaje con hidrolizados de quitosana y MBS (0.25 + 0.05 g.L$ respectivamente), sugiriendo que la inducción de resitencia sistémica juega un papel importante como mecanismop de defensa del tomate contra el ataque de Fusarium oxysporum f.sp lycopersicil (FOL). Se midierojn algunos mecanismos enzimáticos relacionados con la defensa en...
Available micronutrients in agricultural soils of Tenerife (Canary Islands). I.: copper and zinc - Fernández Falcón, Marino; Borges Pérez, A.; Pérez Francés, J. F.; Borges, Andrés A.; López Carreño, I.
A study about available Cu and Zn contents and the influence of some soil properties on the availability of these micronutrients for crops has been carried out in most of the agricultural zones of the Island of Tenerife (Canary Islands).
The mean Cu content was 4.75 mg L-$ (AAAc-EDTA extractable Cu), 22.13% of soil presented values considered as marginals (1-2 mg L-$ Cu), and 6% contained levels below the value estimated as critical (1 mg L-$ Cu). Only 3.64% of analyzed soils showed high Cu values (>17 mg L-" (DTPA extractable Zn), a value sensibly higher than that reported by an...
Available micronutrients in agricultural soils of Tenerife (Canary Islands). II; Iron and manganese - Borges Pérez, A.; Fernández Falcón, Marino; Pérez Francés, J. F.; Borges, Andrés A.
Available Fe and Mn contents and the influence of some soil properties on the availability of these micronutrients for crops were studied in most of the agricultural zones of the island of Tenerife (Canary Islands).
The mean Fe content was 110.4 mg L $ (AAAC-EDTA extractable Fe), about a third lower than that reported by FAO for other regions. 10.64% of the soils presented Fe values below the considered critical level (30 mg L$). The mean Mn content was 67.1 mg L$ (DTPA extractable Mn), almost twice that reported at international level by FAO. Only 0.28% of the soils showed values...
Induced resistance to Fusarian wilt of banana by menadione sodium bisulphite treatments - Borges, Andrés A.; Borges-Pérez, Andrés; Fernández Falcón, Marino
The soilborne fungus Fusarium oxysporum f.sp. cubense is the causal agent of banana vascular wilt disease named Panama disease and one of the most serious threats to banana crops worldwide. A water-soluble addition compound of vitamin K3, menadione sodium bisulphite (MSB), first studied as a plant growth regulator, has recently been shown to induce resistance against Panama disease. Effective fungicides are not yet available to control this fatal disease. Here we report on two independent long-term experiments leading to the enhanced resistance response induced by MSB. The results demonstrated that MSB is an effective resistance activator in banana, and a...
Menadione sodium bisulphite: a novel plant defence activator enhances local and systemic resistance to infection by Leptosphaeria maculans in oilseed rape - Borges, Andrés A.; Cools, H. J.; Lucas, John A.
Pretreatment of the first true leaves of oilseed rape plants (Brassica napus cv. Bristol) with menadione sodium bisulphite (MSB) locally and systemically induced resistance, as shown by reduced lesion size and number, to infection by the fungal pathogen Leptosphaeria maculans, the causal agent of stem canker. Using a known systemic activator of salicylic acid-dependent PR-1 induction, acibenzolar-S-methyl (BTH; S-methylbenzo[1,2,3]thiadiazole-7-carbothiate) as a comparison, real-time PCR expression analysis of genes encoding a pathogenesis-related protein 1 (PR-1) and an ascorbate peroxidase (APX) demonstrated a systemic enhancement of APX expression in MSB-pretreated plants, with no effect on PR-1 expression, suggesting augmented reactive oxygen species...