نتایج جستجو برای: total alkaloid
تعداد نتایج: 806307 فیلتر نتایج به سال:
Please cite this article in press as: Li, Y.; et The highly efficient asymmetric total synthesis of indole alkaloid, ( )-corynantheidol, containing a 2,4,5trisubstituted piperidine core, was achieved using a new version of the one-pot azaelectrocyclization reaction. The formal synthesis of ( )-corynantheidine was also achieved using the common synthetic intermediate for these corynantheines. 20...
A total synthesis of the immunosuppressive alkaloid (-)-FR901483 (1) has been described. The intriguingly azatricyclic structure of 1 was constructed by the semipinacol-type rearrangement and intramolecular Schmidt reaction of an azido cyclohexanone derivative. This strategy provides a distinctive and competitive approach to the natural product 1.
Allowable limits for cereal ergot alkaloids in livestock feeds are being re-examined, and the objective of this study was to compare nutrient digestibility, growth performance and carcass characteristics of ram lambs fed a range of alkaloid concentrations, including the maximum currently allowed in Canada (2 to 3 ppm). Four pelleted diets were fed: control, with no added alkaloids; 930; 1402; a...
بررسی اثر کادمیوم و نیکل بر الگوی تولید آلکالوئیدها در گیاه پروانش (Catharanthus roseus (L.) G. Don)
Tropical plant, Catharanthus roseus contains worthy alkaloids such as vinblastine and ajmalicine. Since amount and pattern of alkaloid production could be affected by different environmental conditions, the effect of two elements of cadmium and nickel were investigated. Plants in the greenhouse conditions using a chemically inert substrate were cultivated and in a complete randomized block desi...
A new asymmetric total synthesis of a phenanthroindolizidine alkaloid (S)-tylophorine is reported, which features a catalytic asymmetric allylation of aldehydes and an unexpected one-pot DMAP promoted isocyanate formation and Lewis acid catalyzed intramolecular cyclization reaction. In addition, White's direct C-H oxidation catalyst system converting monosubstituted olefins to linear allylic ac...
The first total synthesis of the tetracyclic alkaloid (-)-acutumine is described. Key reactions include an asymmetric ketone allylation mediated by Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, and the Lewis acid-promoted cyclization of an amine onto an alpha,beta-unsaturated dimethyl ketal.
The second total synthesis of Brevisamide, a marine cyclic ether alkaloid from Karenia brevis, is reported. This streamlined synthesis proceeds in 21 steps, 14 steps longest linear sequence, in 5.2% overall yield and features a key SmI(2) reductive cyclization step to access the tetrasubstituted pyran core.
A highly stereoselective total synthesis of the alkaloid natural product welwitindolinone A isonitrile has been completed. The synthesis utilizes a chloronium ion mediated semi-pinacol rearrangement to simultaneously install the C10 quaternary center and neopentyl chlorine and a novel anionic cyclization to construct the spiro-oxindole with complete stereocontrol.
The first total synthesis of Aplidiopsamine A, a rare 3H-pyrrolo[2,3-c]quinoline alkaloid from the Aplidiopsis confluata, has been achieved following the proposed biosynthesis. This biomimetic synthesis requires only five steps and proceeds in 20.8% overall yield. Biological evaluation across large panels of discrete molecular targets identified that Aplidiopsamine A is a highly selective PDE4 ...
The total synthesis of the architecturally complex Daphniphyllum alkaloid (-)-calyciphylline N has been achieved. Highlights of the synthesis include a Et2AlCl-promoted, highly stereoselective, susbtrate-controlled intramolecular Diels-Alder reaction, a transannular enolate alkylation, an effective Stille carbonylation/Nazarov cyclization sequence, and a high-risk diastereoselective hydrogenati...
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