- Desymmetrization of acid anhydride with asymmetric esterification catalyzed by chiral phosphoric acid
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Asymmetric desymmetrization of σ-symmetric acid anhydrides was achieved with chiral phosphoric acid as a Br?nsted acid catalyst. The key of success was finding of benzhydrol and 2,2-diphenylethanol as the nucleophiles of choice. The corresponding half esters were obtained in good yields with high selectivity.
- Yamada, Ken-ichi,Oonishi, Akinori,Kuroda, Yusuke,Harada, Shingo,Kiyama, Hiroki,Yamaoka, Yousuke,Takasu, Kiyosei
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supporting information
p. 4098 - 4100
(2016/08/18)
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- A Diels-Alder macrocyclization enables an efficient asymmetric synthesis of the antibacterial natural product abyssomicin C
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An efficient and highly diastereoselective intramolecular Diels-Alder reaction is the basis of a concise asymmetric synthesis of the potent antibacterial natural product abyssomicin C (see formula). The complexity of the target structure was reduced to three fragments and required two carbonyl addition reactions to achieve key bond formations. (Figure Presented).
- Zapf, Christoph W.,Harrison, Bryce A.,Drahl, Carmen,Sorensen, Erik J.
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p. 6533 - 6537
(2007/10/03)
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- Highly enantioselective catalytic thiolysis of prochiral cyclic dicarboxylic anhydrides utilizing a bifunctional chiral sulfonamide
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(Chemical Equation Presented) A catalytic desymmetrization is achieved for various prochiral dicarboxylic anhydrides with yields of 87-100% and ee values of 83-98% through the title reaction (see scheme; Bn = benzyl). The bifunctional effect of the chiral sulfonamide catalyst was clarified on the basis of unsuccessful asymmetric induction by using the related chiral sulfonamides.
- Honjo, Takashi,Sano, Shigeki,Shiro, Motoo,Nagao, Yoshimitsu
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p. 5838 - 5841
(2007/10/03)
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- Synthetic routes to the stereoisomers of 2,4-dimethylpentane-1,5-diol derivatives
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Five different routes to every stereoisomer of non-symmetric derivatives of 2,4-dimethylpentanedioic acid and/or of O-monoprotected 2,4-dimethylpentane- 1,5-diols, which are common building blocks for the total synthesis of many polypropionates, have been investigated. Alkylation of the lithium enolate of N-propanoylpseudoephedrine turned out to be the most appropriate method, in connection with the synthesis of fragment C1-C5 of amphidinolide K.
- Mas, Gemma,González, Llu?sa,Vilarrasa, Jaume
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p. 8805 - 8809
(2007/10/03)
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- Synthesis of (-)-Probetaenone I: Structural Confirmation of Biosynthetic Precursor of Betaenone B
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(-)-Probetaenone I (1) has been synthesized by an intramolecular Diels-Alder reaction and, thereby, its structure has been clearly confirmed; in the biosynthesis of betaenone B (2) the stereochemistry of the C-8 hydroxylation of (1) was proved to involve retention of configuration.
- Miki, Shokyo,Sato, Yoshihiro,Tabuchi, Hiroyasu,Oikawa, Hideaki,Ichihara, Akitami,Sakamura, Sadao
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p. 1228 - 1229
(2007/10/02)
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- Enantiotopic-group Differentation. Catalytic Asymmetric Ring-opening of Prochiral Cyclic Acid Anhydrides with Methanol, using Cinchona Alkaloids
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Asymmetric ring-opening of prochiral acid anhydrides (1) with methanol has been achieved by a catalytic quantity of cinchona alkaloids (2).The product, the optically active half-ester (3), has been subjected to functional-group-selective reduction to give the optically active lactones (5).The reaction rate of the ring-opening and the extent of selectivity are dependent on the nature of the reaction medium, the polarity of solvent, and substrate concentration.By selecting the reaction conditions, an enantiometric excess of up to 70percent has been obtained.The kinetic isotope effect and other mechanistic investigations suggest that the reaction proceeds via general-base catalysis by the quinuclidine moiety of the base (2), and that the relative configuration of the C-9 hydroxy group with respect to the C-8 quinuclidine amino function determines the selectivity of the reaction.
- Hiratake, Jun,Inagaki, Minoru,Yamamoto, Yukio,Oda, Jun'ichi
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p. 1053 - 1058
(2007/10/02)
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- An Asymmetric Synthesis of Lactones from Cyclic Acid Anhydrides with Chiral Binaphthyldiamines
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Asymmetric ring opening of the cyclic acid anhydrides cis-2,3-6 with the axially dissymmetric binaphthyldiamines (S)-1a-d and subsequent esterification gave diastereomeric mixtures of the amide-esters 7a-h.Successive reduction of the ester group and ring closure by hydrolysis afforded (-)-cis-2,4-dimethyl-δ-valerolactone (8, 92percent e.e.), (-)-mevalonolactone (9, 58percent e.e.)(+)-3-isopropyl-δ-valerolactone (10, 42percent e.e.), and (+)-2,3-methylene-γ-butyrolactone (11, 46percent e.e).Through kinetic resolution of the racemic anhydride trans-2, (-)-trans-2,4-dimethyl-δ-valerolactone (12) was yielded in a 74percent e.e., whose absolute configuration was established to be 2R,4R.
- Kawakami, Yukio,Hiratake, Jun,Yamamoto, Yukio,Oda, Jun'ichi
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p. 693 - 698
(2007/10/02)
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- SYNTHESIS OF BOTH THE ENANTIOMERS OF LARDOLURE, THE AGGREGATION PHEROMONE OF THE ACARID MITE, LARDOGLYPHUS KONOI
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Both the enantiomers of lardolure were synthesized in 100 percent optical purity and 99.6 percent diastereomeric purity by use of Frater's diastereoselective alkylation as the key-step.Since (1R,3R,5R,7R)-enantiomer showed the same ORD sign and bioactivity as those shown by the natural pheromone, the structure of lardolure was established unambiguously as (1R,3R,5R,7R)-1,3,5,7-tetramethyldecyl formate.
- Mori, Kenji,Kuwahara, Shigefumi
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p. 5539 - 5544
(2007/10/02)
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- Macrocyclic Pyrrolizidine Alkakoid Analogues. Synthesis and Stereochemistry of (12R,14S)-and (12S,14R)-12,14-Dimethyl-1,2-didehydrocrotalanine. X-Ray Molecular Structure of the (12S,14R)-Isomer
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Treatment of (+)-retronecine (1) with meso-2,4-dimethylglutaric anhydride followed by lactonisation via the pyridine-2-thiol esters yielded (12R,14S)-(3) and (12S,14R)-dimethyl-1,2-didehydrocrotalanine (4).These pyrrolizidine alkaloid analogues were separated by column chromatography.The absolute configuration of the acid portion of each analogue was established by a seguence of two chemoselective reactions to afford optically active tetrahydro-3,5-dimethyl-2H-pyran-2-one.An X-ray crystal structure analysis confirmed the structure and stereochemistry of the (12S,14R)-isomer (4).The ester carbonyl groups of compound (4) are synparallel and directed below the plane of the macrocyclic ring.
- Brown, Kenneth,Burton, Michael,Robins, David J.,Sim, George A.
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p. 1261 - 1266
(2007/10/02)
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- Catalytic Asymmetric Induction from Prochiral Cyclic Acid Anhydrides using Cinchona Alkaloids
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Asymmetric ring-opening of prochiral cyclic acid anhydrides (1) with methanol was effected by a catalytic amount of cinchona alkaloids (2) with an enantiomeric excess of up to 70percent and the product was converted into optically active lactones.
- Hiratake, Jun,Yamamoto, Yukio,Oda, Jun'ichi
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p. 1717 - 1719
(2007/10/02)
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- An Asymmetric Synthesis of 2,4-Dimethylvalerolactone and Mevalonolactone using Chiral Binaphthyldiamine Derivatives
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Axially dissymmetric binaphthyldiamine derivatives formed by asymmetric ring opening of the cyclic anhydrides (3) and (4) ring close on hydrolysis to give (-)-cis-2,4-dimethylvalerolactone (6) and (-)-mevalonolactone (7) in 92percent and 58percent enantiomeric excess (e.e.), respectively; similarly the derivative of the racemic cyclic anhydride (+/-)-(3) ring closes to give (-)-trans-2,4-dimethylvalerolactone with 74percent e.e.
- Kawakami, Yukio,Hiratake, Jun,Yamamoto, Yukio,Oda, Jun'ichi
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p. 779 - 781
(2007/10/02)
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- Stereoselective Synthesis of Alcohols, XI. Double Stereodifferentiation in the Addition of Crotylboronates to Aldehydes: Prelog-Djerassi Lactone
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Addition of the (Z)-crotylboronate 11 to (S)-(+)-α-methylbutyraldehyde (4) resulted in the Cram and Anti-Cram diastereomers 6 and 7.Their ratio depended on the chirality of the boronate component.Hence the formation of the alcohol 7 could be favoured by double stereodifferentiation.Similarly, on addition of the (E)-crotylboronate 12 predominant formation of the isomer 13 could be achieved.These observations formed the basis for a stereoselective synthesis of the Prelog-Djerassi lactone 3.
- Hoffmann, Reinhard W.,Zeiss, Hans-Joachim,Ladner, Wolfgang,Tabche, Susanne
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p. 2357 - 2370
(2007/10/02)
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