The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Zhan Lu - One of the best experts on this subject based on the ideXlab platform.
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enantioselective cobalt catalyzed sequential nazarov cyclization electrophilic fluorination access to chiral α fluorocyclopentenones
Organic Letters, 2018Co-Authors: Heyi Zhang, Biao Cheng, Zhan LuAbstract:A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct Deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones.
Heyi Zhang - One of the best experts on this subject based on the ideXlab platform.
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enantioselective cobalt catalyzed sequential nazarov cyclization electrophilic fluorination access to chiral α fluorocyclopentenones
Organic Letters, 2018Co-Authors: Heyi Zhang, Biao Cheng, Zhan LuAbstract:A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct Deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones.
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Enantioselective Cobalt-Catalyzed Sequential Nazarov Cyclization/Electrophilic Fluorination: Access to Chiral α‑Fluorocyclopentenones
2018Co-Authors: Heyi Zhang, Biao ChengAbstract:A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct Deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones
Beda Marcel Yapo - One of the best experts on this subject based on the ideXlab platform.
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pectins from citrus peel cell walls contain homogalacturonans homogenous with respect to molar mass rhamnogalacturonan i and rhamnogalacturonan ii
Carbohydrate Polymers, 2007Co-Authors: Jeanfrancois Thibault, Beda Marcel Yapo, Patrice Lerouge, Mariechristine RaletAbstract:Abstract Pectins of different structures were extracted from citrus peels with water, oxalate, hot dilute hydrochloric acid and cold dilute sodium hydroxide. Homogalacturonans (HGs) were isolated from the four pectins by mild acid hydrolysis after Deesterification. The study of their macromolecular properties revealed that they have similar number- and weight-average degrees of polymerisation, in the range of 81–117 galacturonic acid units, irrespective of the initial pectin. It was inferred that citrus peel pectins consist of HG strectches of similar lengths whatever the mode of extraction. Rhamnogalacturonan I (RG I) and rhamnogalacturonan II (RG II) were isolated from the oxalate- and the acid-extracted pectins using an endo-1,4-α-polygalacturonase followed by anion-exchange and size-exclusion chromatographies. RG I was composed mainly of arabinose, galactose, galacturonic acid and rhamnose, suggesting the presence of arabinan and/or (arabino)galactan side chains. Debranched RG I (dRG I) was obtained by treating the RG I arising from acid-extracted pectin with endo-1,5-α- l -arabinanase, endo-1,4-β- d -galactanase, α- l -arabinofuranosidase and β- d -galactosidase in admixture. The molar ratios of galacturonic acid to rhamnose of RGs I and dRG I were very close to 1/1, indicating a strict repeating [GalA–Rha] n pattern in the backbone. It is concluded that citrus pectins consist predominantly of HG, with a few RG I and a minor RG II fraction.
Michael R Gretz - One of the best experts on this subject based on the ideXlab platform.
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cell wall development and bipolar growth in the desmid penium margaritaceum zygnematophyceae streptophyta asymmetry in a symmetric world 1
Journal of Phycology, 2009Co-Authors: David S. Domozych, Sarah N Kiemle, Laura Lambiasse, Michael R GretzAbstract:Cell-wall (CW) development in the desmid Penium margaritaceum (Ehrenb.) Breb. was studied using immunofluorescence labeling of living cells with the monoclonal antibodies (mAbs) JIM5 and JIM7, which recognize unesterified and methyl-esterified homogalacturonan (HG), respectively. During cell expansion, HG was secreted in a high-esterified form at a narrow band, called the HG secretion band or HGSB, at the isthmus or the polar tip of a daughter semicell. As newly secreted HG is displaced outward on the cell surface, Deesterification and subsequent calcium (Ca(2+) )-complexing occurred to yield a rigid covering. HG secretion and CW/cell expansion were reversibly inhibited by dark, brefeldin A (BFA), and incubation in 0.24-0.36 M sucrose but were not altered by treatment with actin/microfilament drugs. The HGSB was detected near the nucleus during most cell-cycle events. Centrifugation displaced the nucleus away from the HGSB, but HG synthesis was not affected. HGSB activity was preceded by, and coordinated with, Calcofluor labeling, which suggests that cellulose production in CW/cell-expansion sites was critical to expansion control. In many first-cell-division products, asymmetric patterning of HG was noted in the CW. These asymmetric patterns most likely were a result of timing mechanisms and displacement of the nucleus-HGSB during the cell cycle.
Biao Cheng - One of the best experts on this subject based on the ideXlab platform.
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enantioselective cobalt catalyzed sequential nazarov cyclization electrophilic fluorination access to chiral α fluorocyclopentenones
Organic Letters, 2018Co-Authors: Heyi Zhang, Biao Cheng, Zhan LuAbstract:A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct Deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones.
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Enantioselective Cobalt-Catalyzed Sequential Nazarov Cyclization/Electrophilic Fluorination: Access to Chiral α‑Fluorocyclopentenones
2018Co-Authors: Heyi Zhang, Biao ChengAbstract:A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct Deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones
