- Asymmetric Catalytic Hydrogenations of N-Pyruvoyl-(S)-proline Esters
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Asymmetric catalytic hydrogenations of the entitled compounds were carried out over palladium on charcoal in various solvents to afford N--(S)-proline esters with a d.e.(=diastereoisomeric excess) of up to 59percent.The stereochemistry of the catalytic hydrogenation was explained by the "chelation mechanism." And the effects of temperature and bulkiness of the ester groups on the asymmetric induction were also described.
- Munegumi, Toratane,Fujita, Manabu,Maruyama, Tetsuya,Shiono, Shozo,Takasaki, Michiaki,Harada, Kaoru
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- Ring-Strain Effects in Base-Induced Sommelet–Hauser Rearrangement: Application to Successive Stereocontrolled Transformations
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The base-induced Sommelet–Hauser (S–H) rearrangement of azetidine-2-carboxylic acid ester-derived ammonium salts into 2-aryl-substituted derivatives was demonstrated. The ring-strain of four-membered N-heterocycles enables efficient generation of the desired ylide intermediate and enhances the rate of the S–H rearrangement. The asymmetric version of the rearrangement was characterized by excellent levels of successive chirality transmissions. The regio- and stereo-controlled nucleophilic ring opening of the rearrangement products produced quaternary α-aryl amino acid esters with excellent enantiopurities.
- Tayama, Eiji,Watanabe, Kazutoshi,Matano, Yoshihiro
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supporting information
p. 3631 - 3641
(2016/07/29)
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- Total synthesis of wewakazole B
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Wewakazole B is a novel cyclodecapeptide with highly potent cytotoxic activity isolated from a sample of M. producens collected from the Red Sea. It contains nine common and three modified amino acid residues. The first total synthesis of Wewakazole B was successfully achieved on a gram scale, unambiguously confirming its structure. Notable features include the careful choice of amino acid-protecting groups and the construction of three different substituted oxazoles present in this natural product.
- Long, Bohua,Zhang, Jingzhao,Tang, Xudong,Wu, Zhengzhi
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supporting information
p. 9712 - 9715
(2016/10/31)
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- Convenient and Simple Esterification in Continuous-Flow Systems using g-DMAP
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The utility and applicability of polyethylene-g-polyacrylic acid-immobilized dimethylaminopyridine (g-DMAP) as a catalyst in a continuous-flow system were investigated for decarboxylative esterification. High catalytic activity toward acylation was provided by g-DMAP containing a flexible grafted-polymer structure. During decarboxylation, carboxylic acids and alcohols were converted cleanly using di-tert-butyl dicarbonate (Boc2O) as a coupling reagent, which reduced by-products. In addition, the use of Boc2O resulted in the formation of tert-butyl esters. These esterifications dramatically reduced the reaction time under continuous-flow conditions, with a residence time of approximately 2 min. This highly efficient esterification procedure will provide more practical industrial applications.
- Okuno, Yoshinori,Isomura, Shigeki,Sugamata, Anna,Tamahori, Kaoru,Fukuhara, Ami,Kashiwagi, Miyu,Kitagawa, Yuuichi,Kasai, Emiri,Takeda, Kazuyoshi
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p. 3587 - 3589
(2015/11/17)
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- Solventless mechanosynthesis of N-protected amino esters
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Mechanochemical derivatizations of N- or C-protected amino acids were performed in a ball mill under solvent-free conditions. A vibrational ball mill was used for the preparation of N-protected α- and β-amino esters starting from the corresponding N-unmasked precursors via a carbamoylation reaction in the presence of di-tert-butyl dicarbonate (Boc2O), benzyl chloroformate (Z-Cl) or 9-fluorenylmethoxycarbonyl chloroformate (Fmoc-Cl). A planetary ball mill proved to be more suitable for the synthesis of amino esters from N-protected amino acids via a one-pot activation/esterification reaction in the presence of various dialkyl dicarbonates or chloroformates. The spot-to-spot reactions were straightforward, leading to the final products in reduced reaction times with improved yields and simplified work-up procedures.
- Konnert, Laure,Lamaty, Frederic,Martinez, Jean,Colacino, Evelina
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p. 4008 - 4017
(2014/05/20)
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- Practical one-pot double functionalizations of proline
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Solubilization of proline as the triethylammonium salt allows N-protection (as the Boc, Cbz or Moc derivative) and subsequent esterification or amidation of the carboxy terminus to be performed in an efficient one-pot fashion. Based on this concept, highly practical protocols were developed to prepare a series of proline derivatives (including Pro-Ser dipetides, Weinreb amides and N-protected proline esters), which are important intermediates, for instance, for the synthesis of proline-derived peptides, chiral reagents and catalysts for asymmetric synthesis. Georg Thieme Verlag Stuttgart - New York.
- Huy, Peter,Schmalz, Hans-Guenther
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p. 954 - 960
(2011/05/07)
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- Direct electrochemical α-cyanation of N-protected cyclic amines
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α-Cyanation of N-protected cyclic amines was achieved using a direct electrochemical method. Unsubstituted N-protected cyclic amines were easily cyanated at the α-position using an undivided cell in high yields; moreover, α-cyanation of α′-substituted pyrrolidine and α′-,β′- or γ-substituted piperidines smoothly proceeded in high yield and with high to excellent diastereoselectivity. α-Substituted N-cyano-pyrrolidines and -piperidines were also cyanated at the more substituted position (the α-position) using a divided cell with high yield and high regioselectivity.
- Libendi, Samuel Shikuku,Demizu, Yosuke,Onomura, Osamu
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experimental part
p. 351 - 356
(2009/03/12)
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- Domino catalysis in the direct conversion of carboxylic acids to esters
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The combined use of high concentration conditions, auxiliary bases, and new catalysts allows for the rapid synthesis of sterically hindered carboxylic acid esters at room temperature. Mechanistic analysis indicates the intermediate formation of acid anhydrides and subsequent rate-limiting transformation to the ester products.
- Held,Von Den Hoff,Stephenson,Zipse
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supporting information; experimental part
p. 1891 - 1900
(2009/08/07)
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- Asymmetric [1,2] Stevens rearrangement of (S)-N-benzylic proline-derived ammonium salts under biphasic conditions
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The Stevens rearrangement of (S)-N-benzylic proline-derived ammonium salt with cesium hydroxide in 1,2-dichloroethane is shown to proceed with a high degree of the N-to-C chirality transmission to afford the α-substituted proline derivatives in high enantio-purities. Copyright
- Tayama, Eiji,Nanbara, Shintaro,Nakai, Takeshi
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p. 478 - 479
(2007/10/03)
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- Conformationallly constrained peptidomimetics as β-turn templates and modulators of SH3 domains
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Spirolactam compounds useful as inhibitors of protein-protein interactions modulated by SH3 domains are disclosed. Compounds of the invention are also useful as β-turn mimetics. Also disclosed are libraries of compounds of the invention, pharmaceutical compositions of the compounds of the invention, and methods for using the compounds of the invention to inhibit growth of a cell or to inhibit protein-protein interactions modulated by SH3 domains.
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- Facile new method for preparation of optically active protected proline
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Treatment of L-N-protected 2-amino-5-bromopentanoic acid ester, which was prepared from protected L-glutamic acid, with sodium hydride in tetrahydrofuran (THF) proceeded to give the corresponding protected L-proline in high yield. On the other hand, the reaction of 2-aminobutyric acid derivative with sodium hydride gave the 1-aminocyclopropane-1-carboxylic acid derivative.
- Yamaguchi, Jun-Ichi,Ueki, Masaaki
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p. 621 - 622
(2007/10/03)
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- Dicarbonates: Convenient 4-dimethylaminopyridine catalyzed esterification reagents
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The DMAP (4-dimethylaminopyridine) catalyzed reaction of dialkyl dicarbonates la-e and carboxylic acids 2 afforded the corresponding esters 5 in good yield.
- Takeda,Akiyama,Nakamura,Takizawa,Mizuno,Takayanagi,Harigaya
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p. 1063 - 1066
(2007/10/02)
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- Facile synthesis of tert-butyl ester of N-protected amino acids with tert-butyl bromide
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A facile synthesis of a wide variety of N-benzyloxycarbonyl-amino acid-tert-butyl ester derivatives under mild conditions is described. N-protected amino acids were esterified with tert-butyl bromide in dimethylacetamide as solvent, in the presence of benzyltriethylammonium chloride (BTEAC)and a large excess of potassium carbonate. Many amino Z-acid-Tert-butyl esters that might be difficult to prepare by other methods have been synthesized in high yields by this procedure. The reaction is simple, unexpansive, easily scaled up, and proceeds without observable racemization.
- Chevallet, Pierre,Garrouste, Patrick,Malawska, Barbara,Martinez, Jean
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p. 7409 - 7412
(2007/10/02)
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- TERT-BUTYL ESTERS OF N-PROTECTED AMINO ACIDS WITH TERT-BUTYL FLUOROCARBONATE (Boc-F)
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Tert-butyl fluorocarbonate (Boc-F) is efficiently used for the synthesis of tert-butyl esters of N-protected amino acids.The reaction proceeds at room temperature and under mild conditions in the presence of triethylamine and 4-dimethylamino-pyridine.
- Loffet, A.,Galeotti, N.,Jouin, P.,Castro, B.
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p. 6859 - 6860
(2007/10/02)
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- ISOPROPENYL CHLOROCARBONATE (IPCC) IN AMINO ACID AND PEPTIDE CHEMISTRY: ESTERIFICATION OF N-PROTECTED AMINO ACIDS; APPLICATION TO THE SYNTHESIS OF THE DEPSIPEPTIDE VALINOMYCIN
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Esterification of N-protected α-amino acids was achieved via isopropenyl chlorocarbonate (IPCC) activation.In situ alcoholysis of the unstable mixed anhydride intermediate was catalised by 4-(dimethylamino)pyridine (DMAP).Competing isopropenyl ester formation was negligible when using methylene chloride as the solvent.A variety of esters from primary and secondary alcohols were obtained with good yields (60 to 90 percent), and even the more hindered tertiobutyl alcohol gave acceptable yields under more drastic conditions.The improvement in depsipeptide synthetic methodology is illustrated by preparation of the antibiotic valinomycin, using IPCC for ester bond formation, and BOP reagent for peptide coupling and the last-step cyclisation.
- Zeggaf, Choukri,Poncet, Joel,Jouin, Patrick,Dufour, Marie-Noelle,Castro, Bertrand
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p. 5039 - 5050
(2007/10/02)
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- CONVENIENT ONE-POT ESTERIFICATION OF N-PROTECTED AMINOACIDS VIA ISOPROPENYL CHLOROFORMATE ACTIVATION.
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Activation of N-protected aminoacids by isopropenyl chloroformate leads to esters of primary, secondary and tertiary alcohols with 4-dimethylamino-pyridine as catalyst.
- Jouin, P.,Castro, B.,Zeggaf, C.,Pantaloni, A.,Senet, J.P.,et. al
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p. 1661 - 1664
(2007/10/02)
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- The "Normalizing Factor" for the Toato Mutant chloronerva. XV. - Peptide Analogues of the Phytosiderophore Nicotianamine
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Some peptide analogues of the phytosiderophore nicotianamine, (2S, 3'S, 3"S)-N--azetidine-2-carboxylic acid, have been synthesized from protected amino acids by the EEDQ or the DCC method.They exhibited no biological effect with regard to the phenotypical normalization of the tomato mutant chloronerva.
- Ripperger, H.,Schreiber, K.,Faust, J.
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p. 266 - 272
(2007/10/02)
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- HYDROXYCARBAMOYLALKYLACYLPIPECOLIC ACID COMPOUNDS
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New hydroxycarbamoylalkylacyl derivatives of pipecolic acid which have the general formula STR1 are useful as angiotensin converting enzyme inhibitors.
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- Process for preparing oxazolo?3,2-a!pyrrolo?2,1-c!pyrazine derivatives
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The present invention provides a novel cyclization process useful for the production of the peptide moiety of an ergotalkaloid.
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- PROLINE DERIVATIVES AND RELATED COMPOUNDS
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New proline derivatives and related compounds which have the general formula STR1 are useful as angiotensin converting enzyme inhibitors.
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- CARBOXYACYLPROLINE DERIVATIVES
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New carboxyalkylacylamino acids which are derivatives of proline, pipecolic acid and azetidine-2-carboxylic acid and have the general formula STR1 are useful as angiotensin converting enzyme inhibitors.
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