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Anthony G M Barrett - One of the best experts on this subject based on the ideXlab platform.
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meroterpenoid synthesis via sequential polyKetide aromatization and radical anion cascade triene cyclization biomimetic total syntheses of austalide natural products
Journal of Organic Chemistry, 2019Co-Authors: Philip J Parsons, Anthony G M BarrettAbstract:The first total synthesis of five austalide natural products, (±)-17S-dihydroaustalide K, (±)-austalide K, (±)-13-deacetoxyaustalide I, (±)-austalide P, and (±)-13-deoxyaustalide Q acid, was accomp...
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Meroterpenoid Synthesis via Sequential PolyKetide Aromatization and Radical Anion Cascade Triene Cyclization: Biomimetic Total Syntheses of Austalide Natural Products
2019Co-Authors: Philip J Parsons, Anthony G M BarrettAbstract:The first total synthesis of five austalide natural products, (±)-17S-dihydroaustalide K, (±)-austalide K, (±)-13-deacetoxyaustalide I, (±)-austalide P, and (±)-13-deoxyaustalide Q acid, was accomplished via a series of biomimetic transformations. Key steps involved polyKetide aromatization of a trans,trans-farnesol-derived β,δ-diKetodioxinone into the corresponding β-resorcylate, followed by titanium(III)-mediated reductive radical cyclization of an epoxide to furnish the drimene core. Subsequent phenylselenonium ion induced diastereoselective cyclization of the drimene completed the essential carbon frameworK of the austalides to access (±)-17S-dihydroaustalide K, (±)-austalide K, and (±)-13-deacetoxyaustalide I via sequential oxidations. Furthermore, (±)-13-deacetoxyaustalide I could serve as a common intermediate to be derivatized into other related natural products, (±)-austalide P and (±)-13-deoxyaustalide Q acid, by functionalizing the cyclic lactone moiety
Philip J Parsons - One of the best experts on this subject based on the ideXlab platform.
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meroterpenoid synthesis via sequential polyKetide aromatization and radical anion cascade triene cyclization biomimetic total syntheses of austalide natural products
Journal of Organic Chemistry, 2019Co-Authors: Philip J Parsons, Anthony G M BarrettAbstract:The first total synthesis of five austalide natural products, (±)-17S-dihydroaustalide K, (±)-austalide K, (±)-13-deacetoxyaustalide I, (±)-austalide P, and (±)-13-deoxyaustalide Q acid, was accomp...
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Meroterpenoid Synthesis via Sequential PolyKetide Aromatization and Radical Anion Cascade Triene Cyclization: Biomimetic Total Syntheses of Austalide Natural Products
2019Co-Authors: Philip J Parsons, Anthony G M BarrettAbstract:The first total synthesis of five austalide natural products, (±)-17S-dihydroaustalide K, (±)-austalide K, (±)-13-deacetoxyaustalide I, (±)-austalide P, and (±)-13-deoxyaustalide Q acid, was accomplished via a series of biomimetic transformations. Key steps involved polyKetide aromatization of a trans,trans-farnesol-derived β,δ-diKetodioxinone into the corresponding β-resorcylate, followed by titanium(III)-mediated reductive radical cyclization of an epoxide to furnish the drimene core. Subsequent phenylselenonium ion induced diastereoselective cyclization of the drimene completed the essential carbon frameworK of the austalides to access (±)-17S-dihydroaustalide K, (±)-austalide K, and (±)-13-deacetoxyaustalide I via sequential oxidations. Furthermore, (±)-13-deacetoxyaustalide I could serve as a common intermediate to be derivatized into other related natural products, (±)-austalide P and (±)-13-deoxyaustalide Q acid, by functionalizing the cyclic lactone moiety
Richard F. W. Jackson - One of the best experts on this subject based on the ideXlab platform.
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application of negishi cross coupling to the synthesis of the cyclic tripeptides of4949 iii and K 13
Journal of Organic Chemistry, 2009Co-Authors: Luca Nolasco, Manuel Perez Gonzalez, Lorenzo Caggiano, Richard F. W. JacksonAbstract:Syntheses of the cyclic tripeptides OF4949-III 1 and K-13 2 are reported, in which the Key steps are intermolecular and intramolecular Negishi cross-coupling reactions, respectively. In addition, the synthesis of a protected isomer of K-13 25 is reported. The synthesis of K-13 features a tripeptidic organozinc reagent 11, one of the most highly functionalized such reagents to be described. An O-aryltyrosine derivative 15, prepared by SNAr reaction between Boc-tyrosine and 2-fluorobenzaldehyde, followed by DaKin reaction, iodination, and methylation, is used as a common intermediate for all of the syntheses described. The routes to this class of cyclic tripeptide are among the shortest reported to date and demonstrate the high functional group tolerance of the carbon−zinc bond toward peptide derivatives.
Méndez Zamora Gerardo - One of the best experts on this subject based on the ideXlab platform.
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Germinación de genotipos de pasto banderita (Bouteloua Curtipendula) bajo diferentes presiones osmóticas
2017Co-Authors: Álvarez-holguín Alan, Morales Nieto, Carlos Raúl, Melgoza Castillo Alicia, Méndez Zamora GerardoAbstract:Abstract: The objective was to evalúate the germination rate of sideoats gamma (Bouteloua curtipendula) geno types under different osmotic pressure levels. The genotypes used were El Reno (Re), Niner (Ni), Vaughn (Va), Kansas-6113 (K-13), Kansas-6107 (K-07), ecotype 689 (E-689) and ecotype 592 (E-592). The osmotic agent employed was mannitol. The osmotic pressure levels were; 0.0, -0.7, -1.4 and -2.1 Megapascals (MPa). The variables evaluated were germination percentage (GE), germination speed Índex (GSI), radíele length (RL) and plumule length (PL). The native genotypes (E-592 and E-689) and VA showed the highest resistance to water stress. The genotype K-07 presented the lowest GE and GSI, while Ni did not germinate under -2.1 MPa. Based on the results, E-592, E-689 and Va can be considered for their inclusión on grassland rehabilitation programs. However, due to their speed germination it is recommended to use them in mixture with Re or K-13.Resumen: El objetivo fue evaluar la respuesta de germinación de siete genotipos de pasto banderita (Bouteloua curtipendula), sometidos a diferentes niveles de presión osmótica. Los genotipos utilizados fueron El Reno (Re), Niner (Ni), Vaughn (Va), Kansas-6113 (K-13), Kansas-6107 (K-07), ecotipo 689 (E-689) y ecotipo 592 (E-592). Como agente osmótico se utilizó manitol, los niveles de presión osmótica fueron 0.0, -0.7, -1.4 y -2.1 Mega pasca les. Las variables evaluadas fueron porcentaje de germinación (GE), índice de velocidad de germinación (Vge), longitud de radícula (LR) y plúmula (LP). Los genotipos nativos (E-592 y E-689) y Va presentaron mayor resistencia al estrés hídrico (p < 0.05). El genotipo K-07 presentó menor GE y Vge, mientras que Ni no presentó germinación a -2.1 MPa. Los genotipos E-592, E-689 y Va pueden considerarse en programas de rehabilitación de pastizales. Sin embargo, por su velocidad de germinación se recomienda utilizarlo mezclado con Re o K-13
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Characterization of varieties of sideoats grama grass [Bouteloua curtipendula (Michx.) Torr.] recommended for rangeland restoration
'Revista Mexicana de Ciencias Pecuarias', 2016Co-Authors: Corrales Lerma Raúl, Morales Nieto, Carlos Raúl, Melgoza Castillo Alicia, Sierra Tristán J. Santos, Ortega Gutiérrez, Juan Ángel, Méndez Zamora GerardoAbstract:Con el fin de identificar la mejor variedad de banderita (Bouteloua curtipendula) con el mayor potencial de establecimiento y productividad, se evaluaron cinco variedades comerciales usadas en rehabilitación de pastizales: Niner (Ni), Vaughn (Va), El Reno (Re), Kansas-6107 (K-07) y Kansas-6113 (K-13). Se realizaron dos pruebas bajo condiciones de invernadero con una duración de 77 días. Las variables evaluadas en la prueba unos fueron: emergencia (% EM), densidad de plantas, altura de planta, materia seca del primer corte, altura de rebrote, materia seca de rebrote y supervivencia (% SV). Las variables evaluadas en la prueba dos fueron: longitud de raíz, altura de biomasa aérea y proporción radícula-biomasa aérea. Los datos se analizaron mediante componentes principales, conglomerados y un MANOVA en SAS. Las gráficas de dispersión y dendograma se obtuvieron con MINITAB. Los dos primeros componentes explicaron el 77 % de la variación. Se presentaron diferencias (P
Dirk J Ruiter - One of the best experts on this subject based on the ideXlab platform.
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retinoids strongly and selectively correlate with Keratin 13 and not Keratin 19 expression in cutaneous warts of renal transplant recipients
Archives of Dermatology, 2002Co-Authors: Willeke A M Blokx, J V Smit, Elke M G J De Jong, Monique Link, Peter C M Van De Kerkhof, Dirk J RuiterAbstract:OBJECTIVE: To compare the expression of Keratin (K) 13 and K19 in cutaneous warts of renal transplant recipients (RTRs) and immunocompetent individuals (ICIs). DESIGN: Retrospective, nonrandomized immunohistochemical study. PATIENTS AND METHODS: Specimens from cutaneous warts of RTRs and ICIs were retrieved from the archives of the Department of Pathology, University Medical Center St Radboud, Nijmegen, the Netherlands. Twenty-one warts from RTRs and 21 from ICIs were examined. Nine RTRs (10 specimens) received either systemic acitretin or topical all-trans retinoic acid, and their effect on both Keratins was assessed. MAIN OUTCOME MEASURES: Frequency and expression patterns of K13 and K19 in warts of RTRs vs ICIs and the effect of retinoids. RESULTS: A significantly higher percentage of warts of RTRs expressed K13 compared with warts of ICIs (86% vs 14%, 18 vs 3 cases, respectively; P<.001). In warts of RTRs, retinoid treatment correlated significantly with a particularly strong, segmental K13 expression pattern, which we termed zebroid. Without use of retinoids, K13 was mostly restricted to suprabasal single cells. Keratin 19 was absent in all warts of both patient groups. CONCLUSIONS: Retinoids strongly correlate with K13 in a characteristic zebroid pattern in warts of RTRs, maKing K13 a sensitive marKer for retinoid bioactivity in sKin (lesions) of RTRs. In non-retinoid-treated RTRs, K13 is also frequently found in warts but without the dramatic zebroid pattern noted in retinoid-treated warts.
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retinoids strongly and selectively correlate with Keratin 13 and not Keratin 19 expression in cutaneous warts of renal transplant recipients
Archives of Dermatology, 2002Co-Authors: Willeke A M Blokx, J V Smit, Elke M G J De Jong, Monique Link, Peter C M Van De Kerkhof, Dirk J RuiterAbstract:Objective To compare the expression of Keratin (K) 13 and K19 in cutaneous warts of renal transplant recipients (RTRs) and immunocompetent individuals (ICIs). Design Retrospective, nonrandomized immunohistochemical study. Patients and Methods Specimens from cutaneous warts of RTRs and ICIs were retrieved from the archives of the Department of Pathology, University Medical Center St Radboud, Nijmegen, the Netherlands. Twenty-one warts from RTRs and 21 from ICIs were examined. Nine RTRs (10 specimens) received either systemic acitretin or topical all- trans retinoic acid, and their effect on both Keratins was assessed. Main Outcome Measures Frequency and expression patterns of K13 and K19 in warts of RTRs vs ICIs and the effect of retinoids. Results A significantly higher percentage of warts of RTRs expressed K13 compared with warts of ICIs (86% vs 14%, 18 vs 3 cases, respectively; P zebroid . Without use of retinoids, K13 was mostly restricted to suprabasal single cells. Keratin 19 was absent in all warts of both patient groups. Conclusions Retinoids strongly correlate with K13 in a characteristic zebroid pattern in warts of RTRs, maKing K13 a sensitive marKer for retinoid bioactivity in sKin (lesions) of RTRs. In non–retinoid-treated RTRs, K13 is also frequently found in warts but without the dramatic zebroid pattern noted in retinoid-treated warts.