- Structural permutation of potent cytotoxin, polytheonamide B: Discovery of cytotoxic peptide with altered activity
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Polytheonamide B (1) is an ion-channel forming natural peptide with a d,l-alternating 48 amino acid sequence, which is an exceedingly potent cytotoxin. We recently designed and synthesized a simplified dansylated polytheonamide mimic 2, in which six amino
- Itoh, Hiroaki,Inoue, Masayuki
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- Development of C2-Symmetric Chiral Spirocyclic Phase-Transfer Catalysts: Synthesis and Application to Asymmetric Alkylation of Glycinate Schiff Base
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A class of C2-symmetric chiral spirocyclic phase-transfer catalysts based on tetramethyl-1,1′-spirobiindane scaffold was synthesized from commercially available bisphenol A in 12 steps with 22-25% total yields, which features a more rigid and stable backb
- Xu, Changming,Qi, Yinsheng,Yang, Xinshuang,Li, Xiangfan,Li, Zhenpeng,Bai, Lei
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supporting information
p. 2890 - 2894
(2021/05/05)
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- Counter-rotatable dual cinchona quinuclidinium salts and their phase transfer catalysis in enantioselective alkylation of glycine imines
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Dual cinchona quinuclidinium salts with a diphenyl ether linker were synthesized and used as powerful asymmetric phase transfer catalysts in the α-alkylation of imines of glycine and alanine ester with 0.01-0.1 mol% loading (17 examples, 92-99% ee). Skewed conformers of dual quinuclidiniums at TS were proposed to rationalize their high efficiencyviaDFT calculations.
- Nahm, Keepyung,Oh, Jiin,Park, Jihyeon
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supporting information
p. 6816 - 6819
(2021/07/13)
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- Accelerating Biphasic Biocatalysis through New Process Windows
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Process intensification through continuous flow reactions has increased the production rates of fine chemicals and pharmaceuticals. Catalytic reactions are accelerated through an unconventional and unprecedented use of a high-performance liquid/liquid counter current chromatography system. Product generation is significantly faster than in traditional batch reactors or in segmented flow systems, which is exemplified through stereoselective phase-transfer catalyzed reactions. This methodology also enables the intensification of biocatalysis as demonstrated in high yield esterifications and in the sesquiterpene cyclase-catalyzed synthesis of sesquiterpenes from farnesyl diphosphate as high-value natural products with applications in medicine, agriculture and the fragrance industry. Product release in sesquiterpene synthases is rate limiting due to the hydrophobic nature of sesquiterpenes, but a biphasic system exposed to centrifugal forces allows for highly efficient reactions.
- Huynh, Florence,Tailby, Matthew,Finniear, Aled,Stephens, Kevin,Allemann, Rudolf K.,Wirth, Thomas
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supporting information
p. 16490 - 16495
(2020/07/17)
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- Dimeric cinchona ammonium salts with benzophenone linkers: Enantioselective phase transfer catalysts for the synthesis of α-Amino acids
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Chiral phase transfer catalysts of dimeric cinchona ammonium salts linked with a benzophenone bridge showed high enantioselectivity in the α-Alkylation of a glycinate ester under mild industry-Applicable conditions: 0.5 mol% PTC and near equivalents of al
- Woo, Seunga,Kim, Yong-Gyun,Lim, Baegeun,Oh, Jiin,Lee, Yeonji,Gwon, Hyeri,Nahm, Keepyung
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p. 2157 - 2160
(2018/02/06)
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- Heterogeneous simplified Maruoka phase-transfer catalyst tethered on poly(styrene-co-acrylamide) microsphere: Structure-activity relationship in enantioselective Α-alkylation
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The covalent immobilization of valuable simplified Maruoka catalyst onto poly(styrene-co-acrylamide)microsphere at different locations was developed for the first time through the copolymerization of Maruoka catalyst-functionalized styrene with styrene an
- Feng, Dandan,Wan, Jingwei,Teng, Fei,Ma, Xuebing
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p. 127 - 133
(2017/07/07)
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- Recoverable Dendritic Phase-Transfer Catalysts that Contain (+)-Cinchonine-Derived Ammonium Salts
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Four new phosphorus dendrimeric phase-transfer catalysts are prepared that contain 12 (+)-cinchoninium salts on the surface obtained by the quaternisation of the quinuclidinic N atom. The asymmetric alkylation of a glycinate Schiff base with benzyl bromide is used as a benchmark reaction, and the dendrimeric catalyst that contains an allyl group on the O-9 hydroxy group of the cinchonine units is the most active. The recovery and reuse of the catalyst are possible for five consecutive runs without loss of activity and with only a slight decrease in enantioselectivity. If other electrophiles are used, substituted benzyl bromides give better results than other activated alkyl bromides to afford the corresponding R amino acid derivatives. A comparison of these results with those reported previously for similar cinchoninium salts shows that dendrimers could be a better support than other polymers for this type of organocatalysis.
- Rull, Jordi,Jara, José Juan,Sebastián, Rosa M.,Vallribera, Adelina,Nájera, Carmen,Majoral, Jean-Pierre,Caminade, Anne-Marie
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p. 2049 - 2056
(2016/07/07)
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- Facile one-pot fabrication of a silica gel-supported chiral phase-transfer catalyst - N-(2-cyanobenzyl)-O(9)-allyl-cinchonidinium salt
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A novel type of silica gel-supported cinchona alkaloid-based quaternary ammonium salt was prepared by available one-pot synthesis for the first time through the free radical addition of the sulfhydryl group of 3-mercaptopropyltrimethoxysilane to an exocyc
- Feng, Dandan,Xu, Jinghan,Wan, Jingwei,Xie, Bing,Ma, Xuebing
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p. 2141 - 2148
(2015/04/14)
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- The asymmetric alkylation reaction of glycine derivatives catalyzed by the novel chiral phase transfer catalysts
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Herein a new series of chiral phase transfer catalysts derived from the cinchona alkaloids were synthesized and applied in the asymmetric alkylation of glycine derivatives with high yields and moderate to excellent ee values (39.5-99.7%).
- Wang, Ziyu,Huang, Daorui,Xu, Pei,Dong, Xiaoyang,Wang, Xiaolong,Dai, Zhenya
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supporting information
p. 1067 - 1071
(2015/02/19)
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- Chiral octahedral complexes of CoIII as a family of asymmetric catalysts operating under phase transfer conditions
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Stereochemically inert and positively charged chiral complexes of Co III prepared from Schiff bases derived from chiral diamines and salicylaldehydes were shown to be efficient catalysts of the asymmetric phase transfer benchmark reaction of alkylation of O'Donnell's substrate with alkyl halides. The enantiomeric purities of the reaction products were up to 92%.
- Belokon, Yuri N.,Maleev, Victor I.,North, Michael,Larionov, Vladimir A.,Savel'Yeva, Tat'Yana F.,Nijland, Aike,Nelyubina, Yuliya V.
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p. 1951 - 1955
(2013/09/24)
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- Design, synthesis and functional analysis of dansylated polytheonamide mimic: An artificial peptide ion channel
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We report herein the design, total synthesis, and functional analysis of a novel artificial ion channel molecule, designated as dansylated polytheonamide mimic (3). The channel 3 was designed based on an exceptionally potent cytotoxin, polytheonamide B (1
- Itoh, Hiroaki,Matsuoka, Shigeru,Kreir, Mohamed,Inoue, Masayuki
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p. 14011 - 14018
(2012/10/29)
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- Preparation of chiral amino esters by asymmetric phase-transfer catalyzed alkylations of schiff bases in a ball mill
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The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase-transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified. Copyright
- Nun, Pierrick,Perez, Violaine,Calmes, Monique,Martinez, Jean,Lamaty, Frederic
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p. 3773 - 3779
(2012/04/23)
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- Synthesis and biological evaluation of triazole analogues of antillatoxin
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Antillatoxin 1, a cyclic lipopeptide, is known as an activator of voltage-gated sodium channels and exhibits potent neurotoxicity toward Neuro 2a mouse neuroblastoma cells. To investigate the biological effects of the side-chain structures at C5 and C5′ i
- Goto, Ryosuke,Okura, Ken,Sakazaki, Hayato,Sugawara, Tatsuya,Matsuoka, Shigeru,Inoue, Masayuki
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experimental part
p. 6659 - 6672
(2011/10/01)
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- OPTICALLY ACTIVE QUATERNARY AMMONIUM SALT HAVING AXIAL ASYMMETRY, AND METHOD FOR PRODUCING ALPHA-AMINO ACID AND DERIVATIVE THEREOF BY USING THE SAME
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The present invention discloses an optically active quarternary ammonium salt having axial asymmetry and a method for producing an α-amino acid and a derivative thereof using the same. The optically active quarternary ammonium salt having axial asymmetry
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Page/Page column 25-26
(2010/03/02)
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- Convenient preparation of chiral phase-transfer catalysts with conformationally fixed biphenyl core for catalytic asymmetric synthesis of α-alkyl- and α,α-dialkyl-α-amino acids: application to the short asymmetric synthesis of BIRT-377
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Chiral phase-transfer catalysts (S)-1a, (S)-1b, and (S)-2 with conformationally fixed biphenyl cores were conveniently prepared from the known, easily available (S)-6,6′-dimethylbiphenyl-2,2′-diol 3 and (S)-4,5,6,4′,5′,6′-hexamethoxybiphenyl-2,2′-dicarbox
- Wang, Yong-Gang,Ueda, Mitsuhiro,Wang, Xisheng,Han, Zhenfu,Maruoka, Keiji
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p. 6042 - 6050
(2008/02/08)
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- Effects of aromatic substituents on binaphthyl-based chiral spiro-type ammonium salts in asymmetric phase-transfer reactions
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Spiro-type phase-transfer catalysts prepared from two equivalents of a single binaphthyl subunit were designed and applied to the asymmetric alkylation and direct aldol reactions of a glycine derivative. The effects of the substitution pattern of the bina
- Kano, Taichi,Lan, Quan,Wang, Xisheng,Maruoka, Keiji
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p. 556 - 560
(2008/02/08)
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- Design of chiral phase transfer catalyst with conformationally fixed biphenyl core: Application to asymmetric alkylation of glycine derivatives
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Chiral phase transfer catalysts (S)-1a and (S)-1b with a conformationally fixed biphenyl core were conveniently prepared from the known (S)-6,6′-dimethylbiphenyl-2,2′-diol 2 in five steps. These catalysts, (S)-1a and (S)-1b, are readily applicable to asym
- Wang, Yong-Gang,Maruoka, Keiji
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p. 628 - 632
(2012/12/31)
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- Polymeric chiral phase-transfer catalysts derived from cinchona alkaloids for enantioselective synthesis of α-amino acids
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A series of dimeric/trimeric chiral quaternary ammonium salts derived from cinchona alkaloids were designed as efficient and practical chiral phase-transfer catalysts (PTCs). Presented are the details on the development of the dimeric PTCs for the synthesis of optically active α-amino acid derivatives and the optimization of the reaction variables suitable for the dimeric PTCs. The 1,3-phenyl- and the 2,7-naphthyl-linked dimeric PTCs showed excellent catalytic capability on the reactivity and enantioselectivity in the catalytic phase-transfer alkylation of N-(diphenylmethylene)glycine tert-butyl ester (1). A variety of α-amino acid derivatives were obtained with high enantiopurities using the dimeric PTCs, especially the 2,7-naphthyl-dimer 41, in a very practical manner.
- Lee, Jeong-Hee,Yoo, Mi-Sook,Jung, Ji-Hee,Jew, Sang-sup,Park, Hyeung-geun,Jeong, Byeong-Seon
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p. 7906 - 7915
(2008/02/09)
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- Studies directed toward the synthesis of the scabrosins: validation of a tandem enyne metathesis approach
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A synthetic approach to the scabrosin family of antibiotics using a ruthenium carbene-catalyzed tandem metathesis and?a Pd(II)-catalyzed cyclization is described. The chiral propargyl amino acid is furnished through enantioselective phase-transfer proparg
- Middleton, Mark D.,Peppers, Brian P.,Diver, Steven T.
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p. 10528 - 10540
(2007/10/03)
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- Contrast performance in catalytic ability - New cinchona phase transfer catalysts for asymmetric synthesis of α-amino acids
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Two new cinchona phase transfer catalysts are prepared from dihydrocinchonidine using 13-picenylmethyl bromide and 1-pyrenylmethyl bromide, respectively. A total contrast in catalytic efficiency is observed during the asymmetric alkylation of glycinate es
- Elango, Shanmugam,Venugopal, Murugapillai,Suresh,Eni
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p. 1443 - 1447
(2007/10/03)
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- Enantioselective reactions of tert-butyl glycinate-benzophenone Schiff base catalyzed by chiral phase-transfer catalyst in aqueous media without any organic solvent
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Chiral phase-transfer catalyzed enantioselective alkylations of tert-butyl glycinate-benzophenone Schiff base were investigated in aqueous media without any organic solvent. Reactions in aqueous media smoothly proceeded to give the desired product in high
- Mase, Nobuyuki,Ohno, Takahiro,Morimoto, Hironao,Nitta, Fumito,Yoda, Hidemi,Takabe, Kunihiko
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p. 3213 - 3216
(2007/10/03)
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- Cinchona alkaloid phase-transfer catalysts revisited: Influence of substituted aryl groups on the enantioselectivity of glycine ester enolate alkylation
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We report herein, the influence of substituted aryl groups in quaternary ammonium salts derived from cinchona alkaloids on enantioselectivity of the alkylation of glycine ester enolates.
- Kumar, Sanjeev,Ramachandran, Uma
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p. 7022 - 7028
(2007/10/03)
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- Convenient preparation of highly active phase-transfer catalyst for catalytic asymmetric synthesis of α-alkyl- and α,α-dialkyl- α-amino acids: Application to the short asymmetric synthesis of BIRT-377
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A highly active phase-transfer catalyst was conveniently prepared from the known, easily available (S)-4,5,6,4′,5′,6′- hexamethoxybiphenyldicarboxylic acid. This catalyst exhibited the high catalytic performance (0.01-1 mol %) in the asymmetric alkylation
- Han, Zhenfu,Yamaguchi, Yukako,Kitamura, Masanori,Maruoka, Keiji
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p. 8555 - 8558
(2007/10/03)
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- Asymmetric alkylation of a tert-butyl benzophenone Schiff base derivative in water
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The asymmetric alkylation of a tert-butyl benzophenone Schiff base derivative in water has been successfully carried out in a 'reversed-phase reaction'. The effects of chiral phase-transfer catalysts (PTCs), electrophiles, and reaction conditions (tempera
- Li, Le,Zhang, Zhengpu,Zhu, Xiaoxia,Popa,Wang, Shanwei
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p. 1873 - 1876
(2007/10/03)
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- A new trimeric cinchona alkaloid as a chiral phase-transfer catalyst for the synthesis of asymmetric α-amino acids
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A new trimeric cinchona alkaloid, the quaternary ammonium salt, α,α′,α″-tris[O(9)-allylcinchonidinium-(4- methylphenoxymethyl)]benzene trichloride, has been synthesized and used as an efficient phase-transfer catalyst in asymmetric alkylation of N-(diphen
- Siva, Ayyanar,Murugan, Eagambaram
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p. 2927 - 2933
(2007/10/03)
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- FLUORINE-CONTAINING OPTICALLY ACTIVE QUATERNARY AMMONIUM SALT, METHOD FOR PRODUCING THE SAME AND METHOD FOR PRODUCING OPTICALLY ACTIVE alpha-AMINO ACID DERIVATIVE USING THE SAME
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PROBLEM TO BE SOLVED: To provide a new optically active quaternary ammonium salt having high performances as an axial asymmetry-containing spiro type phase transfer catalyst for an asymmetric alkylation reaction of a glycine derivative, advantageous to the number of catalyst synthetic steps and having the same structure of each ring of the spiro skeleton and to provide a method for producing the same and a method for recovering and purification. SOLUTION: An axial asymmetry-containing spiro type ammonium salt in which a substituent including a perfluoroalkyl group is introduced is excellent as the phase transfer catalyst. The ammonium salt is used for the asymmetric alkylation reaction of the glycine derivative and can then be recovered and purified without deteriorating catalyst performances with a fluorous solvent.
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Page/Page column 29-30
(2008/06/13)
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- Evidence of the electronic factor for the highly enantioselective catalytic efficiency of Cinchona-derived phase-transfer catalysts
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(Chemical Equation Presented) The Cinchona alkaloid-derived quaternary ammonium salts containing 2′-N-oxypyridine and 2′-cyanobenzene moieties were prepared and evaluated as phase-transfer catalysts in the enantioselective alkylation of glycine imine este
- Yoo, Mi-Sook,Jeong, Byeong-Seon,Lee, Jeong-Hee,Park, Hyeung-Geun,Jew, Sang-Sup
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p. 1129 - 1131
(2007/10/03)
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- Development of a recyclable fluorous chiral phase-transfer catalyst: Application to the catalytic asymmetric synthesis of α-amino acids
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A recyclable fluorous chiral phase-transfer catalyst was synthesized and successfully applied for the catalytic asymmetric synthesis of both natural and unnatural α-amino acids. The reaction involves alkylation of a glycine derivative followed by extractive recovery of the chiral phase-transfer catalyst using fluorous solvent.
- Shirakawa, Seiji,Tanaka, Youhei,Maruoka, Keiji
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p. 1429 - 1431
(2007/10/03)
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- Catalytic asymmetric phase-transfer reactions using tartrate-derived asymmetric two-center organocatalysts
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A new highly versatile asymmetric two-center catalyst, tartrate-derived diammonium salt (TaDiAS), was designed and a catalyst library containing more than 70 new two-center catalysts was constructed. A variety of (S,S)- and (R,R)-TaDiAS were easily synthesized from diethyl L- and D-tartrate, respectively, using common and inexpensive reagents under operationally simple reaction conditions. TaDiAS was used in phase-transfer alkylations and Michael additions to afford various optically active α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst (acetal, Ar, and counter anion) for optimization. Recovery and reuse of the catalyst was also possible using simple procedures. The present asymmetric PTC was successfully applied to enantioselective syntheses of serine protease inhibitor aeruginosin 298-A and its analogues.
- Ohshima, Takashi,Shibuguchi, Tomoyuki,Fukuta, Yuhei,Shibasaki, Masakatsu
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p. 7743 - 7754
(2007/10/03)
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- Substituent effect of binaphthyl-modified spiro-type chiral phase-transfer catalysts
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Binaphthyl-modified spiro-type phase-transfer catalysts possessing 4,4′-diaryl substituents are shown to exhibit high asymmetric induction in asymmetric benzylation of benzophenone imine glycine tert-butyl ester under phase-transfer conditions.
- Hashimoto, Takuya,Maruoka, Keiji
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p. 3313 - 3316
(2007/10/03)
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- Symmetrical 4,4′,6,6′-tetraarylbinaphthyl-substituted ammonium bromide as a new, chiral phase-transfer catalyst
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Binaphthyl-modified spiro-type symmetrical phase-transfer catalysts possessing 4,4′,6,6′-tetraaryl substituents are shown to exhibit high asymmetric induction in asymmetric alkylation of benzophenone imine glycine tert-butyl ester under ordinary phase-tra
- Hashimoto, Takuya,Tanaka, Youhei,Maruoka, Keiji
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p. 1599 - 1602
(2007/10/03)
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- Enantioselective syntheses of aeruginosin 298-A and its analogues using a catalytic asymmetric phase-transfer reaction and epoxidation
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We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic part, and counteranion). Copyright
- Ohshima, Takashi,Gnanadesikan, Vijay,Shibuguchi, Tomoyuki,Fukuta, Yuhei,Nemoto, Tetsuhiro,Shibasaki, Masakatsu
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p. 11206 - 11207
(2007/10/03)
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- A New N-Spiro C2-Symmetric Chiral Quaternary Ammonium Bromide Consisting of 4,6-Disubstituted Biphenyl Subunit as an Efficient Chiral Phase-Transfer Catalyst
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A new N-spiro chiral quaternary ammonium bromide has been designed and assembled from optically active 4,6-disubstituted biphenyl subunits. Its utility as an efficient chiral phase-transfer catalyst has been clearly demonstrated by application to the high
- Ooi, Takashi,Kubota, Yasushi,Maruoka, Keiji
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p. 1931 - 1933
(2007/10/03)
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- Highly efficient ortho-fluoro-dimeric cinchona-derived phase-transfer catalysts
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A series of cinchona alkaloid-derived dimeric quaternary ammonium salts were prepared as chiral phase-transfer catalysts by the introduction of various functional groups on the phenyl ligand. Among them, the 2-F-substituted derivative 21 showed the highes
- Park, Hyeung-Geun,Jeong, Byeong-Seon,Yoo, Mi-Sook,Lee, Jeong-Hee,Park, Boon-Saeng,Kim, Myoung Goo,Jew, Sang-Sup
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p. 3497 - 3500
(2007/10/03)
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- New dimeric anthracenyl-derived Cinchona quaternary ammonium salts as phase-transfer catalysts for the asymmetric synthesis of α-amino acids
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New dimeric cinchonidine- and cinchonine-derived ammonium salts which incorporate a dimethylanthracenyl bridge have been prepared and used as phase-transfer catalysts in the asymmetric alkylation of N-(diphenylmethylene)glycine esters in good yields and u
- Chinchilla, Rafael,Mazon, Patricia,Najera, Carmen
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p. 927 - 931
(2007/10/03)
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- C2-symmetric chiral pentacyclic guanidine: A phase-transfer catalyst for the asymmetric alkylation of tert-butyl glycinate schiff base
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The enantioselective alkylation of the Schiff base 2 was carried out in the presence of a novel phase-transfer catalyst, the guanidine-containing pentacyclic compound 1. The product 3 was obtained with enantiomeric excesses of 76-90% (see scheme).
- Kita, Tetsuya,Georgieva, Angelina,Hashimoto, Yuichi,Nakata, Tadashi,Nagasawa, Kazuo
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p. 2832 - 2834
(2007/10/03)
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- Development of new asymmetric two-center catalysts in phase-transfer reactions
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A new asymmetric two-center phase-transfer catalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transfer alkylations and Michael additions to afford the correspo
- Shibuguchi, Tomoyuki,Fukuta, Yuhei,Akachi, Yoko,Sekine, Akihiro,Ohshima, Takashi,Shibasaki, Masakatsu
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p. 9539 - 9543
(2007/10/03)
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- An unusual electronic effect of an aromatic-F in phase-transfer catalysts derived from cinchona-alkaloid.
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[structure: see text] Various N-benzylcinchonidinium salts were prepared to study electronic factors in the catalytic enantioselective phase-transfer alkylation of glycine anion equivalent. An ortho-fluoro substituent on the benzyl group in the quaternary
- Jew, Sang-Sup,Yoo, Mi-Sook,Jeong, Byeong-Seon,Park, Il Yeong,Park, Hyeung-Geun
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p. 4245 - 4248
(2007/10/03)
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- Highly enantioselective and practical cinchona-derived phase-transfer catalysts for the synthesis of α-amino acids
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A new class of naphthalene-based dimeric cinchona alkaloids 1 are very efficient and practical phase-transfer catalysts in the alkylation of a glycine derivative. The mild reaction conditions and the high catalytic efficiency (high yields and ee values) could make these alkaloids practical catalysts in the industrial synthetic process for natural and nonnatural chiral α-amino acids.
- Park, Hyeung-Geun,Jeong, Byeong-Seon,Yoo, Mi-Sook,Lee, Jeong-Hee,Park, Mi-Kyoung,Lee, Yeon-Ju,Kim, Mi-Jeong,Jew, Sang-Sup
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p. 3036 - 3038
(2007/10/03)
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- Trimeric Cinchona alkaloid phase-transfer catalyst: α,α′,α″-tris[O(9)- allylcinchonidinium]mesitylene tribromide
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A trimeric Cinchona alkaloid ammonium salt, α,α′,α″-tris[O(9)- allylcinchonidinium]mesitylene tribromide has been prepared as a novel phase-transfer catalyst. The catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using
- Park, Hyeung-Geun,Jeong, Byeong-Seon,Yoo, Mi-Sook,Park, Mi-Kyoung,Huh, Hoon,Jew, Sang-Sup
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p. 4645 - 4648
(2007/10/03)
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- Design of new, chiral phase-transfer catalysts for practical, catalytic asymmetric synthesis
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Structurally rigid, chiral spiro ammonium salts of type 1 derived from commercially available (S)-binaphthol have been designed as a new C2-symmetric chiral phase-transfer catalyst and successfully applied to the highly efficient, catalytic enantioselective alkylation of tert-butyl glycinate Schiff base under mild phase-transfer conditions to furnish a-alkyl-oc-amino acids and α,α-dialkyl-α-amino acids with excellent enantioselectivity. These ammonium salts have been also utilized for the in situ generation of chiral quaternary ammonium fluorides.
- Maruoka, Keiji
-
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- Asymmetric Alkylation of tert-Butyl Glycinate Schiff Base with Chiral Quaternary Ammonium Salt under Micellar Conditions
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matrix presented The asymmetric alkylation of the tert-butyl glycinate-benzophenone Schiff base 1 with various arylmethyl bromides catalyzed by O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (2) proceeded smoothly under micellar conditions (5 equiv
- Okino, Tomotaka,Takemoto, Yoshiji
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p. 1515 - 1517
(2007/10/03)
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