- Photocatalytic Umpolung Synthesis of Nucleophilic π-Allylcobalt Complexes for Allylation of Aldehydes
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The concept of "umpolung"reactivity of π-allylmetal complexes has been developed as a powerful method for the allylation of aldehydes. This paper describes the photocatalytic umpolung strategy for the synthesis of nucleophilic allylcobalt complexes through a single-electron-transfer (SET) process. This strategy enables the metallaphotoredox allylation of carbonyls with allyl acetate using organic N,N-diisopropylethylamine as the terminal reductant bypassing the use of a stoichiometric amount of metals. Ultraviolet-visible spectroscopy was used to monitor the redox changes of cobalt in the reaction.
- Shi, Caizhe,Li, Fusheng,Chen, Yuqing,Lin, Shuangjie,Hao, Erjun,Guo, Zhuowen,Wosqa, Urwa Tul,Zhang, Dandan,Shi, Lei
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p. 2992 - 2998
(2021/03/09)
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- Enantioselective total syntheses of fr901464 and spliceostatin a and evaluation of splicing activity of key derivatives
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FR901464 (1) and spliceostatin A (2) are potent inhibitors of spliceosomes. These compounds have shown remarkable anticancer activity against multiple human cancer cell lines. Herein, we describe efficient, enantioselective syntheses of FR901464, spliceostatin A, six corresponding diastereomers and an evaluation of their splicing activity. Syntheses of spliceostatin A and FR901464 were carried out in the longest linear sequence of 9 and 10 steps, respectively. To construct the highly functionalized tetrahydropyran A-ring, we utilized CBS reduction, Achmatowicz rearrangement, Michael addition, and reductive amination as key steps. The remarkable diastereoselectivity of the Michael addition was specifically demonstrated with different substrates under various reaction conditions. The side chain B was prepared from an optically active alcohol, followed by acetylation and hydrogenation over Lindlars catalyst. The other densely functionalized tetrahydropyran C-ring was derived from readily available (R)-isopropylidene glyceraldehyde through a route featuring 1,2-addition, cyclic ketalization, and regioselective epoxidation. These fragments were coupled together at a late stage through amidation and cross-metathesis in a convergent manner. Six key diastereomers were then synthesized to probe the importance of specific stereochemical features of FR901464 and spliceostatin A, with respect to their in vitro splicing activity.
- Ghosh, Arun K.,Chen, Zhi-Hua,Effenberger, Kerstin A.,Jurica, Melissa S.
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p. 5697 - 5709
(2014/07/08)
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- A catalytic enantioselective allylation reaction of aldehydes in an aqueous medium
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A modified Yamamoto-Yanagisawa's catalyst (S)-Tol-BINAP·AgNO3 was successfully applied to a catalytic enantioselective allylation reaction of aldehydes in an aqueous system. The reactions with aromatic aldehydes afforded the desired products in
- Loh, Teck-Peng,Zhou, Jian-Rong
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p. 5261 - 5264
(2007/10/03)
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- Chemical library purification strategies based on principles of complementary molecular reactivity and molecular recognition
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A new methodology for solution-phase chemical library synthesis and purification is described. This approach applies fundamental properties of complementary molecular reactivity and recognition (CMR/R) as the basis for a general purification strategy. Specifically, parallel solution-phase reactions are purified by resins containing molecular recognition or molecular reactivity functionalities complementary to those of solution- phase reactants, reagents, and byproducts. When used in sequential or simultaneous combinations, various CMR/R resins remove excess reactants, reagents, and byproducts from solution-phase reaction products, which are isolated in purified form by filtration. Where reactions involve the need to remove byproducts or reagents that do not inherently contain sequestrable functionality, sequestration can be effected by the design and use of tagged reactants or reagents containing artificially-imparted molecular recognition functionality. An extension of this methodology utilizes CMR/R resins as the 'quench phase' instead of a liquid-phase workup commonly used in other library purification strategies. Hence, the essential features of complementary molecular reactivity or molecular recognition required for reaction workup are expressed on resins. The CMR/R library purification strategy is general and highly amenable to automation. Examples are illustrated with amine acylations, the Moffatt oxidation, and the reaction of organometallics with carbonyl compounds.
- Flynn, Daniel L.,Crich, Joyce Z.,Devraj, Rajesh V.,Hockerman, Susan L.,Parlow, John J.,South, Michael S.,Woodard, Scott
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p. 4874 - 4881
(2007/10/03)
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- Method for producing furfuryl alcohols
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A method for producing a furfuryl alcohol useful as an intermediate for producing agricultural chemicals, medicines, perfumes, etc., represented by the general formula (I), STR1 wherein R1 represents a hydrogen atom or a methyl group, and R2 represents an allyl or propargyl group, which comprises reacting a furfural represented by the general formula (II), STR2 wherein R1 has the same meaning as described above, with a halogen compound represented by the general formula, wherein X represents a halogen atom and R2 has the same meaning as described above, in water or a water/organic solvent mixed solvent in the presence of at least one organic quaternary ammonium salt selected from the group consisting of tetra(C2 -C5 alkyl)amonium halide, benzyltri (C2 -C3 alkyl)ammonium chloride, dodecyltrimethylammonium bromide and cetyltrimethylammonium chloride as well as an inorganic ammonium salt and zinc.
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- Production of furfuryl alcohols
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In the production of a furfuryl alcohol of the formula: STR1 wherein R1 is a hydrogen atom or a methyl group and R2 is an allyl or α-methylallyl group, by combining the corresponding furfural of the formula: STR2 wherein R1 is as defined above, with magnesium and allyl chloride or α-methylallyl chloride into a reaction and hydrolysing the resultant product, the improved method wherein tetrahydrofuran or its mixture with at least one aromatic hydrocarbon is used as a reaction medium, and the furfural and allyl chloride or α-methylallyl chloride are simultaneously added to the reaction medium comprising magnesium, whereby the objective furfuryl alcohol is obtained in high yields.
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