- Synthesis and structural studies of new N-(p-toluenesulfonyl)amino acid o-phenolamides
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The synthesis and structural studies of N-(p-Toluenesulfonyl)amino acid o-phenolamides was discussed. The structure and conformation of these amides were established by NMR spectroscopy and x-ray crystallography. Variable temperature experiments showed th
- Aguilar-Castro, Liliana,Tlahuextl, Margarita,Tapia-Benavides, Antonio R.,Tlahuext, Hugo
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- Iodine-Catalyzed Synthesis of Chiral 4-Imidazolidinones Using α-Amino Acid Derivatives via Dehydrogenative N-H/C(sp3)-H Coupling
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An efficient method for the asymmetric synthesis of 4-imidazolidinones via an iodine-catalyzed intramolecular N-H/C(sp3)-H activation of readily available and abundant feedstocks, amino acids, and amines is described. The reaction proceeded under visible light irradiation to afford a variety of 4-imidazolidinone derivatives under mild conditions in moderate to excellent yields. Secondary and tertiary C(sp3)-H bonds were aminated, and various functional groups were tolerated.
- Kanyiva, Kyalo Stephen,Tane, Marina,Shibata, Takanori
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p. 12773 - 12783
(2019/09/09)
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- Metal-Free N–H/C–H Coupling for Efficient Asymmetric Synthesis of Chiral Dihydroquinoxalinones from Readily Available α-Amino Acids
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We have developed a method for the synthesis of dihydroquinoxalinones via intramolecular N–H/C–H coupling using hypervalent iodine. The starting materials were prepared from inexpensive and readily available aniline and amino acid derivatives. Various functional groups were tolerated to give multisubstituted dihydroquinoxalinones in moderate to excellent yields. The chirality of the amino acid was transferred to the desired target compound without a loss of enantiomeric excess. Preliminary mechanistic studies indicated that the reaction proceeds via an ionic mechanism.
- Kanyiva, Kyalo Stephen,Horiuchi, Masashi,Shibata, Takanori
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p. 1067 - 1070
(2018/03/06)
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- Oxazoline derivatives tagged with tosylated amino acids as recyclable organocatalysts for enantioselective allylation of aldehydes
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A series of amino acid-based oxazoline compounds have been prepared and successfully applied to the enantioselective allylation reaction of aldehydes. The fine-tuning of the structure of the oxazolines led to (S,S)-4 as an efficient organocatalyst which gave homoallyl alcohols in good yield (up to 90%) and excellent ee (up to 99%) for a wide range of substrates including aromatic, hetero-aromatic and α,β-unsaturated aldehydes. The chiral organocatalyst was synthesized in three easy steps with an overall 88% yield and successfully recycled for up to three cycles. On the basis of the experimental observations and NMR studies, a probable mechanism was proposed for this reaction.
- Ghosh, Debashis,Sadhukhan, Arghya,Maity, Nabin Ch.,Abdi, Sayed H. R.,Khan, Noor-Ul H.,Kureshy, Rukhsana I.,Bajaj, Hari C.
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p. 12257 - 12265
(2014/03/21)
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- Synthetically amenable amide derivatives of tosylated-amino acids as organocatalysts for enantioselective allylation of aldehydes: Computational rationale for enantioselectivity
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A phenylalanine derived chiral amide is developed that serves as an effective organocatalyst for the reaction of allyltrichlorosilane with aryl, hetero-aryl and α,β-unsaturated aldehydes to afford the desired homoallylic alcohols in good yield (up to 90%)
- Ghosh, Debashis,Sahu, Debashis,Saravanan,Abdi, Sayed H. R.,Ganguly, Bishwajit,Khan, Noor-Ul H.,Kureshy, Rukhsana I.,Bajaj, Hari C.
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p. 3451 - 3460
(2013/06/05)
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- Oxazoline-based organocatalyst for enantioselective strecker reactions: A protocol for the synthesis of levamisole
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A chiral oxazoline-based or-ganocatalyst has been found to efficiently catalyze asymmetric Strecker reactions of various aromatic and aliphatic N-benzhydrylimines with trime-thylsilyl cyanide (TMSCN) as a cyanide source at -20°C to give α-aminoni-triles in high yield (96%) with excellent chiral induction (up to 98% ee). DFT calculations have been performed to rationalize the enantioselective formation of the product with the organo-catalyst in these reactions. The organo-catalyst has been characterized by single-crystal X-ray diffraction analysis, as well as by other analytical methods. This protocol has been extended to the synthesis of the pharmaceutically important drug molecule levamisole in high yield and with high enantioselectivity.
- Sadhukhan, Arghya,Sahu, Debashis,Ganguly, Bishwajit,Khan, Noor-Ul H.,Kureshy, Rukhsana I.,Abdi, Sayed H.R.,Suresh,Bajaj, Hari C.
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p. 14224 - 14232
(2013/11/06)
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- C2-symmetric recyclable organocatalyst for enantioselective Strecker reaction for the synthesis of α-amino acid and chiral diamine-an intermediate for APN inhibitor
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Recyclable chiral amide-based organocatalyst 5 efficiently catalyzed asymmetric Strecker reaction of various aromatic and aliphatic N-benzhydrylimines with ethyl cyanoformate as cyanide source at -10 °C to give a high yield (95%) of α-aminonitriles with excellent chiral induction (ee, up to 99%) with the added advantage of recyclability. Based on experimental observations a probable mechanism was proposed for this reaction. This protocol with catalyst 5 was extended for the synthesis of (R)-phenylalanine and pharmaceutically important drug intermediate (R)-3-phenylpropane-1,2-diamine in high yield with high enantioselectivity.
- Saravanan,Sadhukhan, Arghya,Khan, Noor-Ul H.,Kureshy, Rukhsana I.,Abdi, Sayed H. R.,Bajaj, Hari C.
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p. 4375 - 4384
(2012/06/30)
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- Enantiomers of all-cis-5-(4-bromophenyl)-4-tert-butoxycarbonyl-2- methoxycarbonylpyrrolidine: Preparative HPLC separation and acylative kinetic resolution of the racemate
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The fundamental possibility of acylative kinetic resolution of racemic heterocyclic amines was demonstrated by the example of all-cis-5-(4-bromophenyl) -4-tert-butoxycarbonyl-2-methoxycarbonylpyrrolidine. Individual enantiomers (ee >99%) were obtained in
- Chulakov, Evgeny N.,Gruzdev, Dmitry A.,Levit, Galina L.,Kudryavtsev, Konstantin V.,Krasnov, Victor P.
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p. 1683 - 1688
(2013/02/23)
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- Modular amino acids-based chiral ligands for copper-catalyzed enantioselective conjugation addition of diethylzinc to cyclic enones
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New amino acid-based modular chiral ligands were readily synthesized and used to catalyze the asymmetric conjugate addition of Et2Zn to various cyclic enones in the presence of a variety of copper sources. Moderately high ee of up to 72% were o
- Gou, Shaohua,Judeh, Zaher M. A.
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p. 105 - 112
(2011/11/04)
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- Amino acid-derived hydroxamic acids as chiral ligands in the vanadium catalysed epoxidation
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New sulfonamide-derived hydroxamic acids 7-11 have been developed as chiral ligands for the V-catalysed asymmetric epoxidation, showing high reactivity at subzero temperatures and moderate to good enantioselectivity. The strong accelerating effect exhibited by the ligands of this type can be attributed to the sulfonamide functionality. A range of cinnamyl type allylic alcohols were epoxidised with up to 74% ee. The Royal Society of Chemistry 2005.
- Malkov, Andrei V.,Bourhani, Zainaba,Kocovsky, Pavel
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p. 3194 - 3200
(2007/10/03)
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- Synthesis and structure of lower rim C-linked N-tosyl peptidocalix[4]arenes
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Chiral p-tert-butylcalix[4]arenes functionalized at the lower rim with amino acid residues have been prepared. The 1H and 13C NMR spectra indicate that the macrocycles preferably adopt a cone conformation. Calix[4]arenes bearing amin
- Sdira, Sofiane Ben,Felix, Caroline P.,Giudicelli, Marie-Beatrice A.,Seigle-Ferrand, Pascal F.,Perrin, Monique,Lamartine, Roger J.
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p. 6632 - 6638
(2007/10/03)
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- Wolff rearrangement of diazo ketones derived from N-p-tolylsulfonyl-protected α- and β-amino acids
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Diazo ketones derived from N-p-tolylsulfonyl (tosyl)-protected α- and β-amino acids have been synthesized and their diazo decomposition under standard Wolff rearrangement conditions, PhCO2Ag-Et3N-MeOH, has been investigated. It is observed that, under these conditions, several different reaction pathways, including direct carbene N-H insertion, are possible. The reaction is markedly affected by the N-protecting group, the substrate structure and solvent. For those diazo ketones derived from N-tosyl-protected β-amino acids, the diazo decomposition with anhydrous THF as solvent and PhCO2Ag dissolved in Et3N as catalyst gives the corresponding 5-substituted pyrrolidinones in excellent yields.
- Wang, Jianbo,Hou, Yihua
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p. 1919 - 1923
(2007/10/03)
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- New easily accessible chiral indole ligands
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An efficient and large-scale synthesis of indoles 3 and 4 bearing in 2-position opitically active substituents has been carried out according to the methodology introduced by Fuerstner.Furthermore, starting from indole-2-carbaldeyde, 6, the corresponding chiral indole Schiff bases 7, 8 and 9 have been synthesized.The cobalt complex, prepared from 9 and cobalt(II) acetate, has been shown to catalyze the reduction of acetophenone with NaBH4 in an e. e. of 22percent.
- Cozzi, Pier Giorgio,Prati, Gian Paolo,Umani-Ronchi, Achille
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p. 403 - 406
(2007/10/03)
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- Effect of the 7-Amino Substituent on the Inhibitory Potency of Mechanism-Based Isocoumarin Inhibitors for Porcine Pancreatic and Human Neutrophil Elastases: A 1.85-Angstroem X-ray Structure of the Complex between Porcine Pancreatic Elastase and 7--4-chloro-...
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A series of new acyl, urea, and carbonate derivatives of 7-amino-4-chloro-3-methoxyisocoumarin were synthesized and evaluated as irreversible inhibitors of human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE).Inhibition of HNE is directly related to the hydrophobicity of the substituent on the 7-amino group.The N-Tos-Phe derivative (19) is the best HNE inhibitor with a second-order rate constant kobs/ = 200 000 M-1s-1.The closest analogue in this series, the 3,3-diphenylpropionyl derivative 5, had kobs/ = 130 000 M-1s-1 with HNE.In contrast to the Tos-Phe derivative 19, phenylacetyl derivative 2 and carbonates 22 and 25 gave extremely stable enzyme-inhibitor complexes with deacylation half-lives longer than 48 h with both elastases.N-Phenylurea derivative 25 was the best inhibitor for PPE with a second-order rate constant kobs/ = 7300 M-1s-1.The crystal structure of a complex of PPE with N-tosyl-Phe derivative 19 was determined at 1.85 Angstroem resolution and refined to a final R factor of 16.9percent.The isocoumarin forms an acyl enzyme with Ser-195, while His-57 is near the inhibitor, but not covalently linked.The Tos-Phe makes a few hydrophobic contacts with the S' subsites of PPE, but appears to be interacting primarily with itself in the PPE structure.This region of HNE is more hydrophobic and modeling indicates that the inhibitor would probably make additional contacts with the enzyme.
- Hernandez, Maria A.,Powers, James C.,Glinski, Jan,Oleksyszyn, Jozef,Vijayalakshmi, J.,Meyer, Edgar F.
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p. 1121 - 1129
(2007/10/02)
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- A practical access to optically pure (S)-1-octyn-3-ol
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A highly efficient resolution of (±)-1-octyn-3-ol through recrystallization of the diastereomeric esters has been achieved by using N-(p-toluenesulfonyl)-(S)-phenylalanyl chloride as resolving reagent. The method provides a facile and economical entry to
- Hashimoto,Kase,Suzuki,Yanagiya,Ikegami
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p. 833 - 839
(2007/10/02)
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