The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
M. Mahmun Hossain - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
Organic letters, 2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sharif A. Asad, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, Sharif Asad, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield
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One-Pot Enantioselective Synthesis of Tryptophan Derivatives via Phase-Transfer Catalytic Alkylation of Glycine Using a Cinchona-Derived Catalyst
Synlett, 2012Co-Authors: Robert Todd, Matthew Huisman, Sarah Oehm, Nazim Uddin, M. Mahmun HossainAbstract:Tryptophans are building blocks for many natural products. This paper describes the enantiospecific synthesis of ring-A substituted tryptophan derivatives from commercially available Gramines using chiral phase-transfer conditions. This one-pot reaction avoids protecting/deprotecting the indolylic nitrogen of Gramine by choosing a chemoselective quaternization reagent, 4-(trifluoro-methoxy)benzyl bromide, to produce an electrophilic salt intermediate, which is subsequently alkylated in good yield with high enantiomeric excess.
Luis J Corcuera - One of the best experts on this subject based on the ideXlab platform.
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increase in Gramine content in barley infested by the aphid schizaphis graminum r
Phytochemistry, 1999Co-Authors: Juan A Velozo, Rodrigo I Alvarez, Gerald A Wachter, Barbara N Timmermann, Luis J CorcueraAbstract:The kinetics of accumulation of Gramine were measured in three aphid infested and non-infested cultivars of barley (Hordeum vulgare; cvs. Frontera, Libra and Acuario). After 6 days of infestation Gramine content increased 10-fold in the cvs. Libra and Acuario, while in the cv. Frontera it only doubled. The maximum level found in infested cv. Acuario was 50% of the level observed in non-infested plants of the cv. Frontera. Therefore, in the cvs. Libra and Acuario Gramine content is mainly an inducible response, while it is mainly constitutive in the cv. Frontera. This increase in Gramine may be of significance in resistance to aphids.
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Release of Gramine from the surface of barley leaves
Phytochemistry, 1993Co-Authors: Hideya Yoshida, Hisaaki Tsumuki, Katsuo Kanehisa, Luis J CorcueraAbstract:Abstract Gramine, an indole protoalkaloid found in barley leaves, is toxic to mammals, insects and plants. A time course experiment, in which barley leaves were dipped into 0.1 M hydrogen chloride-ethanol (7:3 v/v) for 1–60 sec, suggested that some Gramine was on
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effect of environment on Gramine content in barley leaves and susceptibility to the aphid schizaphis graminum
Phytochemistry, 1991Co-Authors: M L Salas, Luis J CorcueraAbstract:Abstract Barley seedlings grown under different enviromnental conditions were infested with aphids. The population growth rate of the greenbug Schizaphis graminum decreased in seedlings maintained at temperatures above 25°. Plants grown with longer photoperiods were more resistant to aphids. Gramine concentration increased only in the second (youngest) leaf with high temperatures and photoperiod of 16 hr. The content in the first (oldest) leaf remained constant in all conditions. Water stress did not affect Gramine content and aphid population growth rate in a cultivar with high alkaloid content. Changes in the levels of CO 2 exchange and water potential were similar in both barley cultivars grown at higher temperatures. It is suggested that barley seedlings grown under high temperatures and long photoperiod are more resistant to aphids, because these factors caused an increase in Gramine concentration in the youngest leaves.
Matthew Huisman - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
Organic letters, 2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sharif A. Asad, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, Sharif Asad, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield
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One-Pot Enantioselective Synthesis of Tryptophan Derivatives via Phase-Transfer Catalytic Alkylation of Glycine Using a Cinchona-Derived Catalyst
Synlett, 2012Co-Authors: Robert Todd, Matthew Huisman, Sarah Oehm, Nazim Uddin, M. Mahmun HossainAbstract:Tryptophans are building blocks for many natural products. This paper describes the enantiospecific synthesis of ring-A substituted tryptophan derivatives from commercially available Gramines using chiral phase-transfer conditions. This one-pot reaction avoids protecting/deprotecting the indolylic nitrogen of Gramine by choosing a chemoselective quaternization reagent, 4-(trifluoro-methoxy)benzyl bromide, to produce an electrophilic salt intermediate, which is subsequently alkylated in good yield with high enantiomeric excess.
Qing-nian Cai - One of the best experts on this subject based on the ideXlab platform.
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xenobiotic metabolism of plant secondary compounds in the english grain aphid sitobion avenae f hemiptera aphididae
Pesticide Biochemistry and Physiology, 2013Co-Authors: Maoxin Zhang, Xiao-qin Sun, Tingting Fang, Xuguo Zhou, Qing-nian CaiAbstract:Plant secondary compounds have been documented to be deleterious to insects and other herbivores in diverse ways. In this study, the effect of catechol (phenolics), Gramine (alkaloid) and L-ornithine-HCI (non-protein amino acid) on the activities of xenobiotic metabolizing enzymes in English grain aphid, Sitobion avenae, was evaluated. Phase I enzymes investigated in this study included carboxylesterase (CarE), and oxidoreductase, whereas Phase II enzymes were represented by glutathione S-transferase (GST). In general, CarE and GST activities in S. avenae were positively correlated with the concentration of plant secondary compounds in artificial diets. Oxidoreductase activity, however, displayed a different profile. Specifically, peroxidase (POD) and polyphenol oxidase (PPO) activities in S. avenae were positively correlated with concentrations of dietary catechol and Gramine, respectively, whereas catalase (CAT) activity was significantly suppressed by the higher concentration of catechol, Gramine and L-ornithine-HCl. These combined results suggest that CarE and GST in S. avenae are key enzymes to breakdown a broad spectrum of plant secondary compounds, whereas oxidoreductase, including PPO and POD, degrades specific groups of plant secondary compounds.
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Sensitivity of nlgst1-1 dsRNA pre-fed BPHs to the diets containing Gramine.
2013Co-Authors: Xiao-qin Sun, Maoxin Zhang, Bing Ling, Yu Jin, Qing-ming Qin, Qing-nian CaiAbstract:Gramine was dissolved in artificial diets at the indicated concentrations (GR1 = 12.5 µg/ml). BHPs that had been pre-fed on diets containing 0 (0.8 µg/ml GFP-dsRNA, used as control), 0.2 (dsRNA1), 0.4 (dsRNA2) and 0.8 (dsRNA3) µg/ml nlgst1-1 dsRNA for 3 day were transferred to new diets with the indicated concentrations of Gramine and to the normal control diet without dsRNA and Gramine. The dsRNA pre-fed BPHs were continually reared on these new diets for an additional 3 days in the controlled growth chambers (90% r.h., 28°C, 14 hr photoperiod). The mortalities of the dsRNA pre-fed BPHs transferred to the new diets were plotted at day 4 (A), day 5 (B) and day 6 (C) post feeding. Data represent the means ± SD from three independent experiments with triplicate groups examined for each treatment in each experiment. *and **indicate significance at P
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Gramine content in various rice cultivars.
2013Co-Authors: Xiao-qin Sun, Maoxin Zhang, Bing Ling, Yu Jin, Qing-ming Qin, Qing-nian CaiAbstract:Gramine content was extracted from brown planthopper (BPH)-resistant and BPH-susceptible rice varieties at the seedling (A) and tillering (B) stages. The Gramine content was determined by HLPC approach as described in Materials and Methods. Data represent the means ± standard deviation (SD) from three independent experiments with triplicate samples (each cultivar containing 10 seedling or tillering rice plants) examined. ***indicates significance at P
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Detoxification of Gramine by the cereal aphid Sitobion avenae.
Journal of Chemical Ecology, 2009Co-Authors: Qing-nian Cai, Yazhong Cao, Ying Han, Xin ZhaoAbstract:Secondary metabolites play an important role in host plant resistance to insects, and insects, in turn, may develop mechanisms to counter plant resistance mechanisms. In this study, we investigated the toxicity of Gramine to the cereal aphid Sitobion avenae and some enzymatic responses of S. avenae to this alkaloid. When S. avenae fed on an artificial diet containing Gramine, mortality occurred in a dose-dependent manner. The LC50 of Gramine was determined to be 1.248 mM. In response to Gramine, S. avenae developed increased activities of carboxylesterase and glutathione S-transferase, two important detoxification enzymes. The activities of both enzymes were positively correlated with the concentration of dietary Gramine. In addition, the activities of peroxidase and polypheolic oxidase, two important oxidoreductase enzymes in S. avenae, increased in response to Gramine; however, catalase activity decreased when insects were exposed to higher levels of dietary Gramine. The potential role of Gramine in host plant resistance and S. avenae counter-resistance is discussed.
Sarah Oehm - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
Organic letters, 2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sharif A. Asad, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield.
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Total Synthesis of Tryprostatin B: Synthesis and Asymmetric Phase-Transfer-Catalyzed Reaction of Prenylated Gramine Salt
2018Co-Authors: Matthew Huisman, Mizzanoor Rahaman, Sarah Oehm, Sherwin Novin, Arnold L. Rheingold, Sharif Asad, M. Mahmun HossainAbstract:A concise and efficient total synthesis of microtubule inhibitor tryprostatin B (1) is described. The key step is the preparation of a diprenylated Gramine salt 9a. In this step, the prenyl group is incorporated at the 2-position of the indole moiety by direct lithiation of the Boc-protected Gramine. We also developed and optimized the asymmetric phase-transfer-catalyzed reaction with salt 9a to provide the C2-prenyl tryptophan intermediate 2 resulting in 93% enantiomeric excess (ee) and 65% yield. The total synthesis of 1 is done in six steps with 35% overall yield
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One-Pot Enantioselective Synthesis of Tryptophan Derivatives via Phase-Transfer Catalytic Alkylation of Glycine Using a Cinchona-Derived Catalyst
Synlett, 2012Co-Authors: Robert Todd, Matthew Huisman, Sarah Oehm, Nazim Uddin, M. Mahmun HossainAbstract:Tryptophans are building blocks for many natural products. This paper describes the enantiospecific synthesis of ring-A substituted tryptophan derivatives from commercially available Gramines using chiral phase-transfer conditions. This one-pot reaction avoids protecting/deprotecting the indolylic nitrogen of Gramine by choosing a chemoselective quaternization reagent, 4-(trifluoro-methoxy)benzyl bromide, to produce an electrophilic salt intermediate, which is subsequently alkylated in good yield with high enantiomeric excess.
