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Pancratistatin
Pancratistatin (PST) is a natural compound initially extracted from spider lily, a Hawaiian native plant of the family AmaryllidaceaeShnyder, S. D.; Cooper, P. A.; Millington, N. J.; Gill, J. H.; Bibby, M. C. Sodium Pancratistatin 3,4-O-Cyclic Phosphate, a Water-Soluble Synthetic Derivative of Pancratistatin, Is Highly Effective in a Human Colon Tumor Model. ''J. Nat. Prod.'' 2008, 71, 321-324. (AMD). Occurrence Pancratistatin occurs naturally in Hawaiian spider lily, a flowering plant within the family Amaryllidaceae. Pancratistatin is mostly found in the bulb tissues of spider lilies. It has been shown that the enrichment of atmospheric CO2 can enhance the production of antiviral secondary metabolites, including pancratistatin, in these plants. Pancratistatin can be isolated from the tropical bulbs of ''Hymenocallis littoralis'' in the order of 100 to 150 mg/kg when bulbs are obtained from the wild type in Hawaii. However, the compound has to be commercially extracted f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Samuel Danishefsky
Samuel J. Danishefsky (born March 10, 1936) is an American chemist working as a professor at both Columbia University and the Memorial Sloan-Kettering Cancer Center in New York City. Birth and education Samuel J. Danishefsky was born in 1936 in the United States. He completed his B.S. from Yeshiva University in 1956. He earned his Ph.D. in chemistry from Harvard University in 1962 with Peter Yates (chemist), Peter Yates, which partially overlapped with a National Institutes of Health postdoctoral fellowship in the laboratory of Gilbert Stork at Columbia University. Academic career After completing his PhD, he became professor at the University of Pittsburgh, where he eventually attained the rank of University Professor and taught until 1979. From 1979 to 1993, he was a professor at Yale University, where he rose to the rank of Sterling Professor of Chemistry. By 1991 he was sharing his time with Memorial Sloan-Kettering Cancer Center as director of the Laboratory for Cancer Re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider Lily '', a genus of about 20–30 species of South African plants in the family Amaryllidaceae
{{Plant common name ...
Spider lily is the common name for a number of different plant species within the family Amaryllidaceae which belong to the following genera: * ''Crinum'', a genus of about 180 species of perennial plants in the family Amaryllidaceae found along the sides of streams and lakes in tropical and subtropical areas worldwide, including South Africa * ''Hymenocallis'', a genus of plants in the family Amaryllidaceae * ''Lycoris'', a genus of 13–20 species of flowering plants in the family Amaryllidaceae, formerly often treated in the family Liliaceae * ''Nerine ''Nerine'' (nerines, Guernsey lily, Jersey lily, spider lily) is a genus of flowering plants belonging to the family (biology), family Amaryllidaceae, subfamily Amaryllidoideae. They are bulbous perennial plant, perennials, some evergreen, asso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoquinoline Alkaloids
Isoquinoline alkaloids are natural products of the group of alkaloids, which are chemically derived from isoquinoline. They form the largest group among the alkaloids. Isoquinoline alkaloids can be further classified based on their different chemical basic structures. The most common structural types are the benzylisoquinolines and the aporphines.Bettina Ruff: ''Chemische und biochemische Methoden zur stereoselektiven Synthese von komplexen Naturstoffen.'' Verlag Logos, Berlin 2012, , S. 8. () According to current knowledge, a total of about 2500 isoquinoline alkaloids are known nowadays, which are mainly formed by plants.Jennifer M. Finefield, David H. Sherman, Martin Kreitman, Robert M. Williams: ''Enantiomere Naturstoffe: Vorkommen und Biogenese.'' In: ''Angewandte Chemie.'' Wiley-VCH, Weinheim 2012, doi:10.1002/ange.201107204, S. 4905–4915. Known examples Morphin - Morphine.svg, Morphine Codein - Codeine.svg, Codeine Papaverin - Papaverine.svg, Papaverine Berbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Sources Of Anti-cancer Agents
Plant sources of anti-cancer agents are plants, the derivatives of which have been shown to be usable for the treatment or prevention of cancer in humans. Background In the 1950s, scientists began systematically examining natural organisms as a source of useful anti-cancer substances. It has been argued that "the use of natural products has been the single most successful strategy in the discovery of novel medicines". Plants need to defend themselves from attack by micro-organisms, in particular fungi, and they do this by producing anti-fungal chemicals that are toxic to fungi. Because fungal and human cells are similar at a biochemical level it is often the case that chemical compounds intended for plant defence have an inhibitory effect on human cells, including human cancer cells. Those plant chemicals that are selectively more toxic to cancer cells than normal cells have been discovered in screening programs and developed as chemotherapy drugs Research and development process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bischler–Napieralski Reaction
The Bischler–Napieralski reaction is an intramolecular electrophilic aromatic substitution reaction that allows for the cyclization of β-arylethylamides or β-arylethylcarbamates. It was first discovered in 1893 by August Bischler and , in affiliation with Basle Chemical Works and the University of Zurich. The reaction is most notably used in the synthesis of dihydroisoquinolines, which can be subsequently oxidized to isoquinolines. Mechanisms Two types of mechanisms have appeared in the literature for the Bischler–Napieralski reaction. Mechanism I involves a dichlorophosphoryl imine-ester intermediate, while Mechanism II involves a nitrilium ion intermediate (both shown in brackets). This mechanistic variance stems from the ambiguity over the timing for the elimination of the carbonyl oxygen in the starting amide. In Mechanism I, the elimination occurs with imine formation ''after'' cyclization; while in Mechanism II, the elimination yields the nitrilium intermediate ''pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curtius Rearrangement
The Curtius rearrangement (or Curtius reaction or Curtius degradation), first defined by Theodor Curtius in 1885, is the thermal decomposition of an acyl azide to an isocyanate with loss of nitrogen gas. The isocyanate then undergoes attack by a variety of nucleophiles such as water, alcohols and amines, to yield a primary amine, carbamate or urea derivative respectively. Several reviews have been published. Preparation of acyl azide The acyl azide is usually made from the reaction of acid chlorides or anydrides with sodium azide or trimethylsilyl azide. Acyl azides are also obtained from treating acylhydrazines with nitrous acid. Alternatively, the acyl azide can be formed by the direct reaction of a carboxylic acid with diphenylphosphoryl azide (DPPA). Reaction mechanism It was believed that the Curtius rearrangement was a two-step processes, with the loss of nitrogen gas forming an acyl nitrene, followed by migration of the R-group to give the isocyanate. However, recent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iodolactonization
Iodolactonization (or, more generally, halolactonization) is an organic reaction that forms a ring (the lactone) by the addition of an oxygen and iodine across a carbon-carbon double bond. It is an intramolecular variant of the halohydrin synthesis reaction. The reaction was first reported by M. J. Bougalt in 1904 and has since become one of the most effective ways to synthesize lactones. Strengths of the reaction include the mild conditions and incorporation of the versatile iodine atom into the product. : Iodolactonization has been used in the synthesis of many natural products including those with medicinal applications such as vernolepin and vernomenin, two compounds used in tumor growth inhibition, and vibralactone, a pancreatic lipase inhibitor. Iodolactonization has also been used by Elias James Corey to synthesize numerous prostaglandins. History Sandra's report of iodolactonization represented the first example of a reliable lactonization that could be used in many dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horner–Wadsworth–Emmons Reaction
The Horner–Wadsworth–Emmons (HWE) reaction is a chemical reaction used in organic chemistry of stabilized phosphonate carbanions with aldehydes (or ketones) to produce predominantly E-alkenes. In 1958, Leopold Horner published a modified Wittig reaction using phosphonate-stabilized carbanions. William S. Wadsworth and William D. Emmons further defined the reaction. In contrast to phosphonium ylides used in the Wittig reaction, phosphonate-stabilized carbanions are more nucleophilic but less basic. Likewise, phosphonate-stabilized carbanions can be alkylated. Unlike phosphonium ylides, the dialkylphosphate salt byproduct is easily removed by aqueous extraction. Several reviews have been published. Reaction mechanism The Horner–Wadsworth–Emmons reaction begins with the deprotonation of the phosphonate to give the phosphonate carbanion 1. Nucleophilic addition of the carbanion onto the aldehyde 2 (or ketone) producing 3a or 3b is the rate-limiting step. If R2 = ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claisen Rearrangement
The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. The heating of an allyl vinyl ether will initiate a ,3sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl, driven by exergonically favored carbonyl CO bond formation (ΔΔHf = -327kcalmol−1). Mechanism The Claisen rearrangement is an exothermic, concerted (bond cleavage and recombination) pericyclic reaction. Woodward–Hoffmann rules show a suprafacial, stereospecific reaction pathway. The kinetics are of the first order and the whole transformation proceeds through a highly ordered cyclic transition state and is intramolecular. Crossover experiments eliminate the possibility of the rearrangement occurring via an intermolecular reaction mechanism and are consistent with an intramolecular process. There are substantial solvent effects observed in the Claisen rearrangement, where polar solvents tend to accelerate the reaction to a greater e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National University Of Seoul
Seoul National University (SNU; ) is a national public research university located in Seoul, South Korea. Founded in 1946, Seoul National University is largely considered the most prestigious university in South Korea; it is one of the three "SKY" universities, denoting the top three institutions in the country. The university has three campuses: the main campus in Gwanak District and two additional campuses in Daehangno and Pyeongchang County. The university comprises sixteen colleges, one graduate school and nine professional schools. The student body consists of nearly 17,000 undergraduate and 11,000 graduate students. According to data compiled by KEDI, the university spends more on its students per capita than any other universities in the country that enroll at least 10,000 students. Seoul National University holds a memorandum of understanding with over 700 academic institutions in 40 countries, the World Bank and a general academic exchange program with the University o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enantiomeric Excess
In stereochemistry, enantiomeric excess (ee) is a measurement of purity used for chiral substances. It reflects the degree to which a sample contains one enantiomer in greater amounts than the other. A racemic mixture has an ee of 0%, while a single completely pure enantiomer has an ee of 100%. A sample with 70% of one enantiomer and 30% of the other has an ee of 40% (70% − 30%). Definition Enantiomeric excess is defined as the absolute difference between the mole fraction of each enantiomer: :\ ee = , F_R - F_S, where :\ F_R + F_S = 1 In practice, it is most often expressed as a percent enantiomeric excess. The enantiomeric excess can be determined in another way if we know the amount of each enantiomer produced. If one knows the moles of each enantiomer produced then: Enantiomeric excess is used as one of the indicators of the success of an asymmetric synthesis. For mixtures of diastereomers, there are analogous definitions and uses for diastereomeric excess an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Staudinger Reaction
The Staudinger reaction is a chemical reaction of an organic azide with a phosphine or phosphite produces an iminophosphorane. The reaction was discovered by and named after Hermann Staudinger. The reaction follows this stoichiometry: :R3P + R'N3 → R3P=NR' + N2 Staudinger reduction The Staudinger reduction is conducted in two steps. First phosphine imine-forming reaction is conducted involving treatment of the azide with the phosphine. The intermediate, e.g. triphenylphosphine phenylimide, is then subjected to hydrolysis to produce a phosphine oxide and an amine: :R3P=NR' + H2O → R3P=O + R'NH2 The overall conversion is a mild method of reducing an azide to an amine. Triphenylphosphine or tributylphosphine are most commonly used, yielding tributylphosphine oxide or triphenylphosphine oxide as a side product in addition to the desired amine. An example of a Staudinger reduction is the organic synthesis of the pinwheel compound 1,3,5-tris(aminomethyl)-2,4,6-triethylbenz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
