- Expedient access to pre-organized α-helix mimetics based on an isocinchomeronic acid core
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A previously reported terephthalamide-based α-helix mimetic was modified by introducing a pyridine nitrogen and converting a tertiary amide to a secondary amide, which afforded a second intramolecular hydrogen bond to further influence the projection of t
- Drennen, Brandon,MacKerell, Alexander D.,Fletcher, Steven
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Read Online
- Cathepsin K inhibitors based on 2-amino-1,3,4-oxadiazole derivatives
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Two new series of hitherto unknown dipeptides, containing an electrophilic nitrile or a non-electrophilic 2-amino-1,3,4-oxadiazole moiety were synthesized and evaluated in vitro as Cathepsin K (Cat K) inhibitors. From 14 compounds obtained, the oxadiazole derivatives 10a, 10b, 10e, and 10g acted as enzymatic competitive inhibitors with Ki values between 2.13 and 7.33 μM. Molecular docking calculations were carried out and demonstrated that all inhibitors performed hydrogen bonds with residues from the enzyme active site, such as Asn18. The best inhibitors (10a, 10b, 10g) could also perform these bonds with Cys25, and 10a showed the most stabilizing interaction energy (?134.36 kcal mol?1) with the active cavity. For the first time, derivatives based in 2-amino-1,3,4-oxadiazole scaffolds were evaluated, and the results suggested that this core displays a remarkable potential as a building block for Cat K inhibitors.
- Gontijo, Talita B.,Lima, Patrícia S.,Icimoto, Marcelo Y.,Neves, Raquel Le?o,de Alvarenga, érika C.,Carmona, Adriana K.,de Castro, Alexandre A.,Ramalho, Teodorico C.,da Silva Júnior, Eufranio N.,de Freitas, Rossimiriam P.
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- Amidation of Aldehydes with Amines under Mild Conditions Using Metal-Organic Framework Derived NiO@Ni Mott-Schottky Catalyst
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Here we report a facile method for the synthesis of nickel oxide-nickel (NiO@Ni) Mott-Schottky catalyst employing metal-organic framework (MOF) as the precursor. A direct amidation protocol of aldehydes with amines has been optimized under mild conditions using NiO@Ni Mott-Schottky catalyst and it shows far better catalytic activity than the NiO?Ni nanoparticles prepared from simple Ni2+ salt under similar reaction conditions. The heterogeneous catalyst is robust, recyclable and efficient to provide comparable yield to costly ligand-based homogeneous Ni catalysts. The scope of the reaction protocol has been explored with variably substituted substrates. The reaction initiates by homolytic cleavage of peroxide and proceeds through radical mechanism.
- Goel, Bharat,Vyas, Ved,Tripathi, Nancy,Kumar Singh, Ajit,Menezes, Prashanth W.,Indra, Arindam,Jain, Shreyans K.
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p. 5743 - 5749
(2020/09/09)
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- Selective conversion of primary amides to esters promoted by KHSO4
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Primary amides, either aliphatic or aromatic, are easily converted to the corresponding esters via reflux in lower primary alcohols in the presence of KHSO4. Secondary amides lead to complicated mixtures under analogous conditions, whereastertiary amides were inert. Use of isopropyl alcohol resulted inthe formation of product atslower rate and lower yieldalong withside products, whereas, use of tertiary alcoholsdid not give successful conversion andallyl and benzyl alcohol provided complex mixtures.
- Sattenapally, Narsimha,Sharma, Jhanvi,Hou, Yuqing
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p. 174 - 183
(2018/09/10)
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- Synthesis of Hydrazones from Amino Acids and their Antimicrobial and Cytotoxic Activities
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Hydrazones 6a–6n were synthesized from different amino acids with various aldehydes under reflux in methanol/ethanol. The structures of synthesized compounds were ascertained by elemental analysis and spectroscopic techniques. A comparative study of the antimicrobial activity and cytotoxicity was carried out of the N-protected amino acids, their esters, hydrazides, and the respective hydrazones, providing good results in cytotoxicity studies.
- Abid, Obaid-Ur-Rahman,Khatoon, Ghamama,Arfan, Muhammad,Sajid, Imran,Langer, Peter,Rehman, Wajid,Rahim, Fazal,Yasir, Muhammad,Waqar, Muhammad,Haleem, Kashif Syed
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p. 1079 - 1087
(2017/09/26)
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- A General and Selective Rhodium-Catalyzed Reduction of Amides, N-Acyl Amino Esters, and Dipeptides Using Phenylsilane
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This article describes a selective reduction of functionalized amides, including N-acyl amino esters and dipeptides, to the corresponding amines using simple [Rh(acac)(cod)]. The catalyst shows excellent chemoselectivity in the presence of different sensitive functional moieties. A selective reduction of functionalized amides, including N-acyl amino esters and dipeptides, to the corresponding amines using simple [Rh(acac)(cod)] is described (see scheme). The catalyst shows excellent chemoselectivity in the presence of different sensitive functional moieties. Even the selective reduction of a secondary amide bond in the presence of a ketone is possible.
- Das, Shoubhik,Li, Yuehui,Lu, Liang-Qiu,Junge, Kathrin,Beller, Matthias
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supporting information
p. 7050 - 7053
(2016/05/19)
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- A new type of chiral-pyridoxamines for catalytic asymmetric transamination of α-keto acids
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A new type of chiral pyridoxamines bearing an adjacent chiral stereocenter has been developed via multi-step synthesis. The pyridoxamines displayed catalytic activity in asymmetric transamination of α-keto acids to give a variety of optically active amino acids in 27–78% yields with 34–62% ee's under very mild conditions. This work provides a synthetic strategy to construct new chiral pyridoxamines using bromopyridine 7 as a key synthon and also represents an early example of the applications of chiral pyridoxamines in asymmetric catalysis.
- Chen, Jianfeng,Zhao, Junyu,Gong, Xing,Xu, Dongfang,Zhao, Baoguo
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supporting information
p. 4612 - 4615
(2016/09/23)
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- Highly efficient dehydrogenative cross-coupling of aldehydes with amines and alcohols
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A common protocol for the synthesis of amides, esters and α-ketoesters via cross dehydrogenative coupling of aldehydes and amines/alcohols has been developed. The method is applicable to a wide variety of alcohols and amines as well as aliphatic and aromatic aldehydes. Also, the use of acetaldehyde for acetylation and ethyl glyoxalate to access 2-oxo-amino esters is presented for the first time.
- Deshidi, Ramesh,Rizvi, Masood Ahmad,Shah, Bhahwal Ali
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p. 90521 - 90524
(2015/11/11)
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- N-heterocyclic carbene-catalyzed oxidative amidation of aldehydes with amines
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The N-heterocyclic carbene (NHC)-catalyzed oxidative amidation of aromatic aldehydes with amines in the presence of N-bromosuccinimide (NBS) as an oxidant has been developed for the synthesis of amides. This amidation strategy is tolerant to both the electronic and the steric nature of the aryl aldehydes employed. The present methodology was extended to chiral amino acid derivatives to generate the corresponding amides in good yields and excellent ee values (>98%).
- Alanthadka, Anitha,Maheswari, C. Uma
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supporting information
p. 1199 - 1203
(2015/04/22)
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- Peptide-catalyzed conversion of racemic oxazol-5(4 H)-ones into enantiomerically enriched α-amino acid derivatives
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We report the development and optimization of a tetrapeptide that catalyzes the methanolytic dynamic kinetic resolution of oxazol-5(4H)-ones (azlactones) with high levels of enantioinduction. Oxazolones possessing benzylic-type substituents were found to perform better than others, providing methyl ester products in 88:12 to 98:2 er. The mechanism of this peptide-catalyzed process was investigated through truncation studies and competition experiments. High-field NOESY analysis was performed to elucidate the solution-phase structure of the peptide, and we present a plausible model for catalysis.
- Metrano, Anthony J.,Miller, Scott J.
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p. 1542 - 1554
(2014/03/21)
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- Copper-catalyzed oxidative amidation of aldehydes with amine salts: Synthesis of primary, secondary, and tertiary amides
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A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug N-acetylprocainamide.
- Ghosh, Subhash Chandra,Ngiam, Joyce S. Y.,Seayad, Abdul M.,Tuan, Dang Thanh,Chai, Christina L. L.,Chen, Anqi
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p. 8007 - 8015,9
(2012/12/12)
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- Copper-catalyzed oxidative amidation of aldehydes with amine salts: Synthesis of primary, secondary, and tertiary amides
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A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug N-acetylprocainamide.
- Ghosh, Subhash Chandra,Ngiam, Joyce S.Y.,Seayad, Abdul M.,Tuan, Dang Thanh,Chai, Christina L.L.,Chen, Anqi
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p. 8007 - 8015
(2013/01/15)
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- Oxidative amidation of aldehydes and alcohols with primary amines catalyzed by KI-TBHP
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Oxidative amidation of aldehydes and alcohols with amines to afford the corresponding amides in excellent yields and ee values over 98% is achieved by using a catalytic amount of KI in combination with TBHP as the external oxidant. This method avoids the use of expensive and/or air-sensitive reagents. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Rajender Reddy,Uma Maheswari,Venkateshwar,Lakshmi Kantam
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supporting information; experimental part
p. 3619 - 3622
(2009/05/07)
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- Enantioselective benzoylation of α-amino esters using (S)-1-benzoyl-2-(α-acetoxyethyl)benzimidazole, a chiral benzimidazolide
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(Chemical Equation Presented) A new chiral benzimidazolide is developed as a nonenzymatic acylating agent for enantioselective benzoylation of racemic α-amino esters. The process is highly efficient, which exhibits uniformly high enantioselectivity for α-amino esters with or without aryl substituents under mild reaction conditions. The chiral benzimidazolide is inexpensive and is easily accessible.
- Karnik, Anil V.,Kamath, Suchitra S.
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p. 7435 - 7438
(2008/02/11)
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- New pseudonucleosides containing chiral oxazolidin-2-ones and Cyclosulfamides as aglycones: Synthesis and antiviral evaluation
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A series of chiral cyclosulfamides and oxazolidinon-2-ones have been synthesized starting from aminoacids. Regioselective substitution of these pseudopyrimidic heterocyles was carried out under Mitsunobu conditions. Best substitution results were obtained by preliminary deprotection of cyclosulfamides and their condensation with β -D-ribofuranose. Chiral oxazolidin-2-ones were coupled directly with D-ribofuranose. All compounds were tested against HSV-2, VV and SV viruses. Two compounds 6b and 6e showed significant activities against HSV-type 1. Copyright Taylor & Francis Group, LLC.
- Bouleghlem, Hocine,Berredjem, Malika,Lecouvey, Marc,Aouf, Nour-Eddine
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p. 1539 - 1542
(2008/09/20)
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- Rate constants for 1,n-hydrogen transfer reactions in some amino acid derived radicals
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Absolute rate constants for 1,n-hydrogen atom transfers in some substituted amino acid derived radicals have been determined in benzene through the use of competitive kinetic experiments. Radicals derived from methyl N-(2-iodobenzoyl)-N-(tert-butyloxycarbonyl)glycinate, -alaninate, -leucinate, -tert-leucinate and -phenylglycinate undergo intramolecular 1,5-hydrogen atom transfer to afford the corresponding α-amino acid ester radicals with rate constants in the range: 1.0-4.3 × 107 s-1 at 80 °C. Where abstractable hydrogen atoms exist in the amino acid side-chain, 1,6- and 1,7-translocations are competitive processes.
- Zeng, Le,Kaoudi, Talbi,Schiesser, Carl H.
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p. 7911 - 7914
(2007/10/03)
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- Simple and Efficient Cleavage Reaction of the Boc Group in Heterocyclic Compounds
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A series of chiral cyclosulfamides have been synthesized by alkaline cyclisation starting from N-benzoylamino acids (Ala, Val, Leu, Phe) derivatives and chlorosulfonyl isocyanate. A simplified and regioselective deprotection of the cyclic compounds (cyclosulfamides) containing the tert-butyloxycarbonyl group (Boc) has been achieved in good yield by fusion under reduced pressure.
- Nadia, Klai,Malika, Berredjem,Nawel, Khettache,MedYazid, Belghit,Zine, Regainia,Aouf, Nour-Eddine
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- New cyanopeptide-derived low molecular weight thrombin inhibitors
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Thrombosis is the result of defective regulation of the hemostasis system. This cardiovascular disorder may lead to deep vein thrombosis, myocardial infarction, and stroke. The majority of current drug research is focused on finding inhibitors of thrombin - the global player in hemostasis. In our work, we emphasize investigation of the marine environment to yield new lead structures from marine organisms like blue-green algae (cyanobacteria). This article deals with the design, syntheses, and inhibition tests of new low molecular weight thrombin inhibitors utilizing cyanopeptides, the secondary metabolites of cyanobacteria with interesting biological activities, as new lead structures. Starting with aeruginosin 98-B (2) as a lead structure, we have developed and synthesized new, selective acting inhibitors of thrombin (RA-1001 and RA-1002), which are suitable targets for further structure-activity studies.
- Radau, Gregor,Gebel, Jana,Rauh, Daniel
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p. 372 - 380
(2007/10/03)
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- Cyanopeptide analogues: New lead structures for the design and synthesis of new thrombin inhibitors
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This contribution deals with the structure-based design and syntheses of the new serine protease inhibitors RA-1001 and RA-1002, which are analogues of the blue-green algae derived cyanopeptide aeruginosin 98-B. Both compounds inhibit thrombin with Ki values of 5.6 μM and 8.7 μM, respectively.
- Radau, Gregor,Stuerzebecher
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p. 729 - 732
(2007/10/03)
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- Dynamic kinetic resolution: Synthesis of optically active α-amino acid derivatives
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Candida antarctica lipase B (Novozyme) is an effective catalyst for the dynamic kinetic resolution of racemic 2-benzyl-4-substituted-5(4H)- oxazolones, in the presence of an alcohol, yielding optically active N- benzoyl amino acid esters. The reaction has been optimised with respect to the solvent and the effect of a catalytic amount of organic base is investigated. (C) 2000 Elsevier Science Ltd.
- Brown, Stuart A.,Parker, Marie-Claire,Turner, Nicholas J.
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p. 1687 - 1690
(2007/10/03)
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- Efficient one-pot formation of amides from benzyl carbamates: Application to solid-phase synthesis
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A convenient one-pot protocol for the conversion of benzyl carbamates to amides is described. The general applicability of the procedure is illustrated using various types of substrates. This new method proceeds rapidly under mild conditions, in good yields, and without noticeable racemization. This protocol was applied to solid-phase synthesis to prepare amides and esters from Merrifield resin-bound carbamates and carbonates. (C) 2000 Elsevier Science Ltd.
- Li, Wen-Ren,Yo, Ying-Chih,Lin, Yu-Sheng
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p. 8867 - 8875
(2007/10/03)
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- Enzymatic Asymmetric Synthesis of α-Amino Acids. Enantioselective Cleavage of 4-Substituted Oxazolin-5-ones and Thiazolin-5-ones
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A general enzymatic asymmetric synthesis of L-α-amino acids has been developed.This method entails the use of the Pseudomonas cepacia lipase (P-30) to catalyze the enantioselective methanolysis of a variety of 4-substituted 2-phenyloxazolin-5-one derivatives in a nonpolar organic solvent to furnish optically active N-benzoyl-L-α-amino acid methyl esters (ee = 66-98 percent), which in turn is subjected to a protease-catalyzed kinetic resolution yielding enantiomerically pure N-benzoyl-L-α-amino acids.This synergistic coupling of two enzymes allows the ready preparation of L-α-amino acids of high enantiopurity in yields greater than 50 percent, an inherent advantage over conventional resolution procedures.Two proteases were found to catalyze the enantioselective hydrolysis of a variety of 4-substituted 2-phenylthiazolin-5-one derivatives to give N-(thiobenzoyl)-L-α-amino acids of high optical purity.
- Crich, Joyce Z.,Brieva, Rosario,Marquart, Peer,Gu, Rui-Lin,Flemming, Steffen,Sih, Charles J.
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p. 3252 - 3258
(2007/10/02)
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- NITROSATION OF PEPTIDE BONDS. CLEAVAGE OF NITROSATED PEPTIDES BY PYRROLIDINE AND α-AMINO ESTERS
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The reaction of several α-amino acids and peptides (containing Gly, L-Ala, L-Leu, L- or DL-Phe, and/or L- or D-Val) with air-diluted nitrogen oxides has been studied to roughly mimic the N-nitrosation of peptide bonds that the contaminated urban air might produce in pulmonary tissues. Most N-protected α-amino acids give practically quantitative yields of N-nitroso derivatives. N-Protected dipeptides afford either dinitrosated peptides, mixtures of di- and mononitrosated compounds, selectively mononitrosated products, or no reaction at all, depending mainly on steric effects. The same trends are observed for some higher peptides.The (poly)nitrosated peptides, which retain the chirality of the starting materials, have been characterized by 1H and 13C NMR spectroscopy and are cleaved by pyrrolidine and amino esters under mild conditions to give (new) amides or peptides plus diazo derivatives.
- Garcia, Jordi,Gonzalez, Javier,Segura, Ramon,Vilarrasa, Jaume
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p. 3121 - 3128
(2007/10/02)
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- ASYMMETRIC SYNTHESIS OF β-LACTAMS. I. THE REACTION OF DIMETHYLKETENE SILYL ACETAL WITH (S)-ALKYLIDENE(1-ARYLETHYL)AMINES PROMOTED BY TITANIUM TETRACHLORIDE
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Asymmetric synthesis of β-lactams by means of the reaction of dimethyl-ketene silyl acetal with (S)-alkylidene(1-arylethyl)amines in the presence of titanium tetrachloride was studied.The extent of the asymmetric induction was in the range of 44-78percent (diastereomeric purity 72-89percent) and the (S)-configuration was turned to be preferentially induced at the 4C position of the resulting β-lactams.
- Ojima, Iwao,Inaba, Shin-ichi
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p. 2077 - 2080
(2007/10/02)
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