- Kendarimide A, a novel peptide reversing P-glycoprotein-mediated multidrug resistance in tumor cells, from a marine sponge of Haliclona sp.
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A novel modulator of multidrug resistance (MDR) in tumor cells, kendarimide A (1), was isolated from an Indonesian marine sponge of Haliclona sp. Compound 1 reversed MDR in KB-C2 cells mediated by P-glycoprotein (P-gp) at a 6 μM concentration, and the chemical structure of 1 was characterized to be a linear peptide composed of N-methylpyroglutamic acid (pyroMeGlu), N-methylated eight-membered cysteinyl-cysteine (ox-[MeCys-MeCys]) together with many N-methyl amino acid residues. The amino acid sequence of 1 was determined by 2D NMR and FAB MS analysis. The absolute configuration of the amino acid residues in 1 except for the MeCys part was determined to be L-form respectively, based on interpretation of the HPLC analysis of Marfey's derivatives of the hydrolysates of 1 and the synthetic method for the pyroMeGlu residue.
- Aoki, Shunji,Cao, Liwei,Matsui, Kouhei,Rachmat, Rachmaniar,Akiyama, Shin-Ichi,Kobayashi, Motomasa
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Read Online
- Synthesis of protected α-amino acids: Via decarboxylation amination from malonate derivatives
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A general and efficient strategy for the synthesis of protected α-amino acids is reported. The method uses malonate derivatives as the starting materials and Cs2CO3 as a base at 60 degrees, giving α-amino acid derivatives in moderate yields by releasing CO2. This methodology shows broad substrate scope (primary and secondary acids), excellent functional group tolerance and high efficiency to give the desired products under mild reaction conditions. It also allows the construction of β and γ-amino acids and other unnatural products.
- Dai, Qipu,Fu, Hui,Hu, Changwen,Li, Peihe,Li, Xiaoying,Wang, Zheng
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p. 4439 - 4446
(2020/10/20)
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- A (1 R, 3 S) -3 - amino-cyclopentanol hydrochloride preparation method (by machine translation)
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The invention discloses a (1 R, 3 S) - 3 - amino-cyclopentanol hydrochloride of the preparation method, the method using chiral carboxylic acid with hydroxylamine to form the amide as chiral source, in copper catalyzed oxidation in the reaction system to rapidly obtain a chiral Diels - alder reaction product, after passes through the reduction reaction and alkaline deprotection reaction, and acidified after reaction to obtain the target product. Chiral inducing reagent chiral carboxylic acid by simple acidification, extraction processing can be reclaimed and reused. This kind of (1 R, 3 S) - 3 - amino-cyclopentanol hydrochloride preparation method has high operation safety and high selectivity, raw materials are easy, and the cost is low, the reaction time is short and simple process flow and the like. (by machine translation)
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- Base catalytic decarboxylation amination preparation method of amino-acid ester/amide
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The invention discloses a base catalytic preparation method of alpha amino-acid ester/amide from beta carbonyl acid, and belongs to the field of organic chemistry. According to the method, malonate is taken as a raw material, single hydrolysis is carried out to obtain beta carbonyl acid, reaction with a hydroxylamine compound is carried out to obtain an acyloxyl carbamic acid ester, and under the effect of an alkali, removing of one molecule carbon dioxide is carried out so as to obtain an alpha amino-acid ester, wherein the process of synthesis of the alpha amino-acid ester/amide is similar to the above process. The raw materials are widely available; operation is simple and convenient; reaction conditions are mild; using of toxic cyanide and derivatives of cyanide, strong oxidizing/reducing agents, and precious metal catalysts in a conventional alpha amino acid synthesis method is avoided; and requirements of the trend of green chemistry development are satisfied.
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Paragraph 0064-0065
(2019/10/10)
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- Ring opening reactions of cyclic sulfamidates. Synthesis of β-fluoroaryl alanines and derivatives of 4,4-difluoroglutamic acid
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Ring opening reactions of 1 with copper complex formed between Cu, TMEDA and BrCF2CO2Et lead to optically active 4,4-difluoroglutamic acid derivatives 11a-d in moderate yields. Reaction of cyclic sulfamidates 1 with fluoro substituted arylmagnesium chlorides proceed via copper catalyzed 1,4-addition of Grignard reagent to dehydroalanine 2, formed in situ. Fluorinated organoznic derivatives were unreactive towards 1 regardless of the reaction conditions; instead product of reaction of 1 with DMF was isolated.
- Bolek, Sylwia,Ignatowska, Jolanta
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- Diastereoselective Synthesis of Unnatural Amino Acids by Alkylation of α- Tert-Butanesulfinamide Auxiliary-Bound Enolates
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A new chiral auxiliary for the diastereoselective alkylation of amino ester enolates that takes advantage of chiral information stored on the enolate side of the amino ester substrate has been developed. Chiral α-sulfinamido esters were alkylated under basic conditions in good yields (up to 90%) and good to high diastereoselectivities (generally >6:1) to provide unnatural mono- and α,α-disubstituted amino acid derivatives. This auxiliary allowed for the ready conversion of ester functionality without the need for esoteric reagents. Furthermore, the auxiliary is easily removed to provide enantiopure amino acids. Computational studies revealed that a chelated transition state governs electrophile addition from the convex face of a transient bicyclic intermediate. This method allows ready access to enantioenriched natural and unnatural amino acids.
- Dwulet, Natalie C.,Zolfaghari, Tina A.,Brown, Molly L.,Cannon, Jeffrey S.
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p. 11510 - 11518
(2018/09/27)
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- Copper nanoparticles catalyzed N-H functionalization: An efficient solvent-free N-tert-butyloxycarbonylation strategy
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A chemoselective transformation of amines to their tert-butyloxycarbonyl (Boc) protected derivatives (NBoc) is described using Cu-NPs under solvent-free conditions. Simple method, rapid reaction rate, mild conditions, tolerance of a wide range of functional groups, excellent yield, ease recovery and high catalytic turnover are the salient features of this approach. tert-Butyloxycarbonylation of chiral amino acid esters and amino alcohols were performed without racemization.
- Deb, Barnali,Debnath, Sudipto,Deb, Anindita,Maiti, Dilip K.,Majumdar, Swapan
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supporting information
p. 629 - 633
(2017/01/25)
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- Towards a universal organocatalyst for the synthesis of enantioenriched phenylalanine derivatives by enantioselective decarboxylative protonation
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Access to enantioenriched non-proteogenic phenylalanine derivatives is described using the enantioselective decarboxylative protonation reaction of amidohemimalonate esters catalysed by various cinchona-based compounds. This study compares the catalytic efficiency as well as the enantioselectivity induced by three types of common organocatalysts, namely thioureas, squaramides and bis-cinchona squaramides. One of the main outcome of this work is the observation of a significant influence of the N-protecting group of the hemimalonate on its interaction with the catalyst. This methodology carried out under mild conditions exhibits good substrate scope and functional group tolerance. A substoichiometric amount of catalyst can also be used in certain cases while affording good yields and selectivities.
- Pigeaux, Morgane,Laporte, Romain,Harrowven, David C.,Baudoux, Jér?me,Rouden, Jacques
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p. 4599 - 4603
(2016/09/23)
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- Non-noble metal-based catalytic of high-efficiency oxidation coupling reaction C-H/C-H preparing β-(hetero) aryl propionic acid derivatives
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The invention relates to a method for efficiently preparing beta-(hybrid)aryl alanine derivative based on non-noble metal catalyzed C-H/C-H oxidative coupling action. Aiming at the defects of the prior art, the invention provides the preparation method of beta-(hybrid)aryl alanine derivative. The preparation method is simpler, more efficient and environmentally friendly than the traditional method, adopts non-noble metal catalysis, adopts alpha-amino acid derivative and (hybrid)aryl methane derivative as starting materials, adopts a mild organic oxidizer, and avoids the using of noble metal salt and strong base, thereby being capable of greatly reducing the cost, synthesis procedures, operation difficulty, hazardous waste and equipment corrosion, and having a good industrial production prospect.
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Paragraph 0029; 0031
(2017/03/24)
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- Symplocin A, a linear peptide from the bahamian cyanobacterium symploca sp. configurational analysis of N, N -dimethylamino acids by chiral-phase HPLC of naphthacyl esters
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The absolute stereostructures of the components of symplocin A (3), a new N,N-dimethyl-terminated peptide from the Bahamian cyanobacterium Symploca sp., were assigned from spectroscopic analysis, including MS, 2D NMR, and Marfey's analysis. The complete a
- Molinski, Tadeusz F.,Reynolds, Kirk A.,Morinaka, Brandon I.
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experimental part
p. 425 - 431
(2012/07/13)
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- Double stereodifferentiation in the catalytic asymmetric aziridination of imines prepared from α-chiral amines
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The catalytic asymmetric aziridination of imines and diazo compounds (AZ reaction) mediated by boroxinate catalysts derived from the VANOL and VAPOL ligands was investigated with chiral imines derived from five different chiral, disubstituted, methyl amines. The strongest matched and mismatched reactions with the two enantiomers of the catalyst were noted with disubstituted methyl amines that had one aromatic and one aliphatic substituent. The synthetic scope for the AZ reaction was examined in detail for α-methylbenzyl amine for cis-aziridines from α-diazo esters and for trans-aziridines from α-diazo acetamides. Optically pure aziridines could be routinely obtained in good yields and with high diastereoselectivity and the minor diastereomer (if any) could be easily separated. The matched case for cis-aziridines involved the (R)-amine with the (S)-ligand, but curiously, for trans-aziridines the matched case involved the (R)-amine with the (R)-ligand for imines derived from benzaldehyde and n-butanal, and the (R)-amine with the (S)-ligand for imines derived from the bulkier aliphatic aldehydes pivaldehyde and cyclohexane carboxaldehyde.
- Huang, Li,Zhang, Yu,Staples, Richard J.,Huang, Rui H.,Wulff, William D.
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p. 5302 - 5313
(2012/05/20)
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- Selective esterifications of primary alcohols in a water-containing solvent
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Oxyma and an oxyma derivative, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate (5b), displayed a remarkable effect on selective esterifications of primary alcohols. A wide range of carboxylic acids could be esterified with primary alcohols by using EDCI, NaHCO3, and Oxyma or Oxyma derivative 5b in 5% H2O-CH3CN. Oxyma derivative 5b is particularly useful, since it could be removed after the reaction via a simple basic or an acidic aqueous workup procedure.
- Wang, Yong,Aleiwi, Bilal A.,Wang, Qinghui,Kurosu, Michio
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supporting information
p. 4910 - 4913,4
(2012/12/12)
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- Selective esterifications of primary alcohols in a water-containing solvent
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Oxyma and an oxyma derivative, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl 2-cyano-2-(hydroxyimino)acetate (5b), displayed a remarkable effect on selective esterifications of primary alcohols. A wide range of carboxylic acids could be esterified with primary alcohols by using EDCI, NaHCO3, and Oxyma or Oxyma derivative 5b in 5% H2O-CH3CN. Oxyma derivative 5b is particularly useful, since it could be removed after the reaction via a simple basic or an acidic aqueous workup procedure.
- Wang, Yong,Aleiwi, Bilal A.,Wang, Qinghui,Kurosu, Michio
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supporting information
p. 4910 - 4913
(2013/01/15)
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- CHEMICAL COMPOUNDS
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The present invention relates to highly functionalized 1,3-diamino-propan-2-ols and pharmaceutically acceptable salts thereof. More specifically, the invention relates to highly functionalized 1,3-diamino-propan-2-ols that are derivatives of the HIV prote
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Page/Page column 43
(2011/02/24)
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- An efficient and chemoselective Br?nsted acidic ionic liquid-catalyzed N-Boc protection of amines
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The first report of a Br?nsted acidic ionic liquid, 1-methylimidazolium tetrafluoroborate [(HMIm)BF4], catalyzed efficient and chemoselective N-Boc protection of various amines using (Boc)2O is presented. Optically pure amino alcohols and amino acid esters were converted efficiently to their corresponding optically pure N-Boc derivatives. The reported method is mild, solvent-free and has the advantages of both homogeneous and heterogeneous catalysis with high product yields, selectivity and ease of product separation.
- Sunitha, Sadula,Kanjilal, Sanjit,Reddy, P. Srinivasa,Prasad, Rachapudi B.N.
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p. 2527 - 2532
(2008/09/19)
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- N-acyl and N-alkoxycarbonyl derivatives of 1H-1,2,3-triazolo-[4,5-c] pyridine; preparation and application
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The N-acylating and N-alkoxycarbonylation ability of the N-substituted 1,2,3-triazolo[4,5-c]pyridines 1a-e have been investigated. The alkoxycarbonyl triazolopyridine derivatives (1c-e) were readily prepared in 81-96% yield (the corresponding tetrafluoroborate > 95%). Triazolo[4,5-c]pyridine (1) has been shown to work as a good leaving group by the formation of amido- and carbamate protected derivatives of primary amines. The method was also successful for the N-tert-butoxycarbonyl (N-BOC) protection of the amino acid, phenylalanine. The synthetic transformations are facilitated by the one-pot preparation of 1a-e followed by the direct reaction with the amines or amino acid. The present method thus offers an efficient and convenient protocol for the in situ preparation of triazolopyridine reagents to be used directly for the protection of amines and amino acids. N-Acyl- and N-alkoxycarbonyl triazolopyridines (1a-e) were readily prepared in 4 steps from 4-aminopyridine (4) by amine protection, pyridine nitration, nitro reduction and diazotizations/cyclizations. All reactions offer the advantages of rapid conversions in high yields under very mild conditions.
- Holt, Jarle,Fiksdahl, Anne
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p. 417 - 423
(2007/10/03)
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- The Baylis-Hillman reaction with chiral α-amino aldehydes under racemization-free conditions
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The Baylis-Hillman reaction with chiral α-amino aldehydes has been revisited. The reaction carried out under the influence of ultrasound avoids the aldehyde racemization almost completely, providing useful chiral substrates which can be used as starting materials for the synthesis of natural products. To demonstrate the synthetic applicability of these adducts, the easy preparation of a bicyclic lactam with an indolizidinic skeleton was accomplished. Georg Thieme Verlag Stuttgart.
- Coelho, Fernando,Diaz, Gaspar,Abella, Carlos A. M.,Almeida, Wanda P.
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p. 435 - 439
(2007/10/03)
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- Synthesis of phenylalanine analogs
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A straight forward synthesis of phenylalanine analogs is described. Cerium ammonium nitrate (CAN) mediated addition of azide to cinnamicester, followed by reaction with sodium acetate aff orded the α-azidocinnamate in moderate yield. Hydrogenation of α-azidocinnamate, followed by BOC, CBZ or Fmoc protection gave phenylalanine analogs. A new approach for synthesizing racemic p-boronophenylalanine analog was also explored.
- Chang, Meng-Yang,Lin, Chun-Yu,Sun, Pei-Pei
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p. 1061 - 1067
(2007/10/03)
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- Chromophoric azo reagents for amino acid and peptide labelling
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Four carboxylic azo dyes, with spectroscopic absorption peaks ranging from 400 to 500 nm, are presented as new markers for amino acid and peptide labelling at their N-terminus. Labelling can also be performed at side-chain residues as is exemplified with lysine and serine. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Fraga, Susana M. B.,Goncalves, Maria S. T.,Moura, Joao C. V. P.,Rani, Kavitha
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p. 1750 - 1760
(2007/10/03)
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- Development of a temporary marker for peptides
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3-[(N,N-Dimethylaminophenyl)-4′-diazenyl]benzoic acid was coupled with several amino acid esters and the product acylated further with Boc. The material thus obtained was then submitted to cleavage by electrolysis and nucleophilic attack in order to evaluate the possibility of using this chromophore as a temporary marker.
- Sameiro,Goncalves,Maia, Hernani L.S.
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p. 1480 - 1485
(2007/10/03)
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- Kinetic resolutions of chiral 2-and-3-substituted carboxylic acids
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One aspect of the present invention relates to a method for the kinetic resolution of racemic and diastereomeric mixtures of chiral compounds. The critical elements of the method are: a non-racemic chiral tertiary-amine-containing catalyst; a racemic or diastereomeric mixture of a chiral substrate, e.g., a cyclic carbonate or cyclic carbamate; and a nucleophile, e.g., an alcohol, amine or thiol. A preferred embodiment of the present invention relates to a method for achieving the kinetic resolution of racemic and diastereomeric mixtures of derivatives of α- and β-amino, hydroxy, and thio carboxylic acids. In certain embodiments, the methods of the present invention achieve dynamic kinetic resolution of a racemic or diastereomeric mixture of a substrate, i.e., a kinetic resolution wherein the yield of the resolved enantiomer or diastereomer, respectively, exceeds the amount present in the original mixture due to the in situ equilibration of the enantiomers or diastereomers under the reaction conditions prior to the resolution step.
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- Kinetic resolutions of chiral 2-and-3-substituted carboxylic acids
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One aspect of the present invention relates to a method for the kinetic resolution of racemic and diastereomeric mixtures of chiral compounds. The critical elements of the method are: a non-racemic chiral tertiary-amine-containing catalyst; a racemic or diastereomeric mixture of a chiral substrate, e.g., a cyclic carbonate or cyclic carbamate; and a nucleophile, e.g., an alcohol, amine or thiol. A preferred embodiment of the present invention relates to a method for achieving the kinetic resolution of racemic and diastereomeric mixtures of derivatives of α- and β-amino, hydroxy, and thio carboxylic acids. In certain embodiments, the methods of the present invention achieve dynamic kinetic resolution of a racemic or diastereomeric mixture of a substrate, i.e., a kinetic resolution wherein the yield of the resolved enantiomer or diastereomer, respectively, exceeds the amount present in the original mixture due to the in situ equilibration of the enantiomers or diastereomers under the reaction conditions prior to the resolution step.
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- Molecular discrimination of N-protected amino acid esters by a self-assembled cylindrical capsule: spectroscopic and computational studies.
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A self-assembled, cylindrical capsule was used to bind N-alpha-protected amino acid esters. The reversible encapsulation was studied using NMR spectroscopy in deuterated mesitylene solution and by computer-aided molecular modeling. BOC-L-alanine alkyl est
- Hayashida, Osamu,Sebo, Lubomir,Rebek Jr., Julius
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p. 8291 - 8298
(2007/10/03)
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- A temporary marker for biological applications
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Having in mind the development of new colour labelled amino acid derivatives, a carboxyl azo dye was coupled to amino acid esters to give the corresponding orange N-acyl derivatives, which were in turn further acylated at their N-terminus with Boc for investigation of the conditions of possible cleavage of the chromophore by electrolysis or with nucleophiles. While difficulties were met with electrolysis owing to competitive reduction of the azo group, cleavage with N,N-diethylaminoethylamine (DEAEA) gave satisfactory results. This allows the use of the chromophore as a temporary marker.
- Sameiro, M,Gon?alves, T,Maia, Hernani L.S
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p. 7775 - 7777
(2007/10/03)
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- Subtilisin-catalyzed synthesis of amino acid and peptide esters. Application in a two-step enzymatic ligation strategy.
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We describe an efficient enzymatic approach to the synthesis of amino acid and peptide esters. The serine protease subtilisin Carlsberg (EC 3.4.21.62) was found to efficiently catalyze the specific formation of C(alpha)-carboxyl 3-hydroxypropyl or 4-hydro
- Liu,Tam
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p. 4157 - 4159
(2007/10/03)
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- An Improved Preparation of Oxazolidin-2-one Chiral Auxiliaries
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Reduction of carbamate-blocked amino esters by lithium borohydride (made in situ from sodium borohydride and lithium iodide) forms chiral 4-substituted oxazolidin-2-ones directly. The presence of iodide in the reaction mixture appears to promote the cyclization of the intermediate alkoxyborohydride. This provides a route to these important chiral auxiliaries, employing less hazardous reagents and simpler reaction conditions than do most existing methods.
- Sudharshan, Manjula,Hultin, Philip G.
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p. 171 - 172
(2007/10/03)
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- SYNTHESIS OF AMINO ACID ESTERS BY PAPAIN
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A wide range of N-Boc-amino acid esters were synthesized from N-Boc-amino acids and alcohol using papain as catalyst.Suitable biphasic reaction mixtures were found for most amino acids to achieve high yield of ester synthesis.With N-Boc-L-aspartic and glutamic acids only the α carbonyl group esterified, without racemisation.
- Cantacuzene, D.,Pascal, F.,Guerreiro, C.
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p. 1823 - 1826
(2007/10/02)
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