- Solvent dependency though not solvate formation in the derivative-derivative resolution of N-formylphenylalanine
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The efficiency of the resolution of N-formylphenylalanine was remarkably improved using (S)-(+)-2-benzylaminobutanol resolving agent in acetone. The efficiency of the resolution strongly depended on the quality of the solvent. Nevertheless, solvate formation did not occur during the process. The nature of the solvent-dependence was studied. The solid-melt binary phase diagram of the diastereomeric salts formed during the resolution by (S)-(+)-2-benzylaminobutanol was measured and discussed. It was recognized that the (S)-(+)-benzylaminobutanol (S)-(+)-N-formylphenylalanine salt exists in two polymorphic modifications. The effect of structurally related chiral and achiral auxiliary reagents in the above resolution was also studied. Thus, (S)-(+)-2-benzylaminobutanol was applied together with an (R)-(+)-1-phenylethylamine auxiliary resolving agent and benzylamine was used as a half-equivalent achiral basic reagent in a Pope-Peachey type resolution of N-formylphenylalanine by (S)-(+)-2-benzylaminobutanol. The results are compared to those obtained by the structurally related (R)-(+)-1-phenylethylamine chiral auxiliary.
- Palovics, Emese,Bereczki, Laura,Marthi, Katalin,Pokol, Gyoergy,Faigl, Ferenc,Fogassy, Elemer
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- Optical resolution of N-formylphenylalanine succeeds by crystal growth rate differences of diastereomeric salts
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Optical resolution of racemic-phenylalanine through its N-formyl derivative with a 1-phenylethylamine resolving agent is an effective procedure. Differential scanning calorimetry, single crystal X-ray diffraction and optical microscopy were used in the investigation of the resolution process. It was found that the thermodynamic properties of the given system would not allow the efficient enantiomer separation. Kinetic effects during the crystal formation have been discovered by the comparison of the crystal morphologies of the two diastereomers. The crystal structure of the less soluble diastereomer (S)-(-)-1-phenylethylammonium (S)-(+)-N-formylphenylalaninate salt has been determined and discussed.
- Bereczki, Laura,Palovics, Emese,Bombicz, Petra,Pokol, Gyoergy,Fogassy, Elemer,Marthi, Katalin
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- Formyloxyacetoxyphenylmethane as an N-Formylating Reagent for Amines, Amino Acids, and Peptides
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Formyloxyacetoxyphenylmethane is a stable, water-tolerant, N-formylating reagent for primary and secondary amines that can be used under solvent-free conditions at room temperature to prepare a range of N-formamides, N-formylanilines, N-formyl-α-amino acids, N-formylpeptides, and an isocyanide.
- Chapman, Robert S. L.,Lawrence, Ruth,Williams, Jonathan M. J.,Bull, Steven D.
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supporting information
p. 4908 - 4911
(2017/09/23)
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- MgI2-chemoselective cleavage for removal of amino acid protecting groups: A fresh vision for peptide synthesis
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In the field of peptide synthesis, the key to a successful access to synthetic targets lies on a pertinent combination of protecting groups. Their choice is directed by their selective removal conditions. We present here the behavior of some of the most used protecting groups in peptide chemistry under experimental cleavage conditions, combining MgI2 with MW irradiation, using 2-Me-THF as a green solvent. In these experimental conditions, the benzyloxycarbonyl protecting group as well as the Merrifield resin can be re-considered in peptide chemistry.
- Berthet, Mathéo,Martinez, Jean,Parrot, Isabelle
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- An aryne-based three-component access to α-aroylamino amides
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Aryne chemistry has recently received widespread attention and isocyanides have been reported as efficient nucleophilic partners in a set of multicomponent transformations. In this study, we demonstrate that tertiary α-monosubstituted α-isocyanoacetamides are efficaciously coupled with water and benzyne to offer a direct and metal-free access to densely functionalized α-benzoylamino amides, without competing with the intramolecular cyclization to 5-aminooxazoles. Despite the formation of the aryl anion as a key intermediate, the reaction displays a stereoconservative course, allowing for the preparation of enantiomerically pure α-benzoylamino amides. Finally, the synthetic utility of the reported MCR was exemplified by the preparation of proglumide, a cholecystokinin antagonist.
- Serafini, Marta,Griglio, Alessia,Viarengo, Sara,Aprile, Silvio,Pirali, Tracey
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p. 6604 - 6612
(2017/08/16)
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- Enantioselective Synthesis of Quaternary Δ4- and Δ5-Dehydroprolines Based on a Two-Step Formal [3+2] Cycloaddition of α-Aryl and α-Alkyl Isocyano(thio)acetates with Vinyl Ketones
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A divergent synthesis of optically active quaternary Δ4- and Δ5-dehydro prolines is developed based on the first catalytic enantioselective conjugate addition of α-substituted isocyano(thio)acetates to vinyl ketones that is general for both α-aryl and α-alkyl isocyano(thio)acetates. The new tetrasubstituted C?N stereocenter is formed without the need of any metal salt due to a bifunctional tertiary amine/squaramide catalyst, featuring a bulky polyaryl sidearm and an unusually short squaramide diamide H???H interatomic distance in the solid state.
- Odriozola, Amaiur,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 12758 - 12762
(2017/09/25)
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- A convenient procedure for N-formylation of amines
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A simple and convenient method for the N-formylation of primary and secondary amines including amino acids has been developed utilizing formamide and sodium methoxide in moderate to excellent yield. This reagent is also utilized for one pot conversion of compounds having amino esters to N-formyl amides.
- Joseph, Sony,Das, Prasenjit,Srivastava, Bindu,Nizar, Hashim,Prasad, Mohan
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p. 929 - 931
(2013/02/25)
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- The influence of molecular structure and crystallization time on the efficiency of diastereoisomeric salt forming resolutions
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Reciprocal resolutions between compounds (racemates and enantiomers) with similar structures have been examined. Amongst structurally similar compounds (so called relative structures) several N-acyl amino acids and amino acid esters were investigated. A part of the resolving agent or the racemic compound could be replaced by an achiral compound with a relative structure and an additive could occasionally improve significantly the efficiency of the resolution. Both the kinetic and the thermodynamic controls were observed as governing factors of the reciprocal resolutions.
- Palovics, Emese,Schindler, Jozsef,Faigl, Ferenc,Fogassy, Elemer
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experimental part
p. 2429 - 2434
(2010/12/25)
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- Application of multicomponent reactions to antimalarial drug discovery. Part 3: Discovery of aminoxazole 4-aminoquinolines with potent antiplasmodial activity in vitro
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The synthesis and antimalarial activity of a novel series of first generation 4-aminoquinoline-containing 2,4,5-trisubstituted aminoxazoles against two strains of the Plasmodium falciparum parasite in vitro is described. A number of compounds significantly more potent than the standard drug chloroquine were identified.
- Musonda, Chitalu C.,Little, Susan,Yardley, Vanessa,Chibale, Kelly
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p. 4733 - 4736
(2008/03/11)
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- An artificial receptor for the intermolecular and enantioselective formation of peptide sheets
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Peptide strands coupled at the C terminus to bis[p(aminomethyl)phenyl] ether allow in CHCl3 solution association of lipophilic N-protected peptides with hydrogen bonds in the mode of antiparallel β-sheets; the enantioselectivity observed with a phenylalanine derivative is characterized by a binding constant ratio of around 15.
- Eblinger, Frank,Schneider, Hans-Joerg
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p. 2297 - 2298
(2007/10/03)
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- Stereoselective synthesis of fused γ-lactams by intramolecular nitrone cycloaddition
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A series of nitrones 5 joined by amides to olefines were prepared in situ from the related aldehydes with N-methylhydroxylamine. The nitrone added intramolecularly to the olefin, and the cycloadditions gave fused γ-lactams 6 stereoselectively. A stereocentre located in positron α to the nitronic functionality 13 completely controls the stereochemical course of the intramolecular cycloaddition, which exclusively affords compound 14 with simultaneous introduction of four stereocentres. The formation of this latter compound was also supported by PM3 calculations. Furthermore, simple heating of unsaturated oxine 17 led to compound 19 via intramolecular oxime olefin cycloaddition.
- Chiacchio, Ugo,Buemi, Giuseppe,Casuscelli, Francesco,Procopio, Antonio,Rescifina, Antonio,Romeo, Roberto
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p. 5503 - 5514
(2007/10/02)
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- Processes and compounds useful for resolving 1-methyl-3-phenylpropylamine
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(R)-1-methyl-3-phenylpropylamine which can be prepared from a mixture containing said compound along with (S)-1-methyl-3-phenylpropylamine by contacting a solution of said compounds or of their soluble salts with an effective amount of a compound of formula I to form a salt of formula II which selectively precipitates from said solution, and wherein R is -COR1, -CONR2R3 or -SO2R4; R1 is H, alkyl, alkoxy, allyloxy, phenyl, phenyloxy, benzyl, benzyloxy, all optionnally substituted , or 2-furanylmethoxy, R2 and R3 may be the same or different and each is independently selected from H, alkyl, phenyl, benzyl, all optionnally substituted and R4 is alkyl, phenyl, benzyl, all optionnally substituted.
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- A New Approach to Asymmetric Synthesis of Polycycles on the Basis of o-Quinodimethane Generation
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The fluoride anion induced 1,4-elimination of 2-phenyl>-3,3-dimethyloxazolidinium salts generates (E,E)-α-alkyl-α'--o-quinodimethane intermediates, which are trapped stereoselectively with dienophiles to give polycycles.Intramolecular cyclization of 2-phenyl>-3,3-dimethyl-4-(R)-methyl-5(R)-phenyloxazolidinium triflate at 0 deg C produces a 3:1 diastereoisomeric mixture of 6--trans-octahydrophenanthrene, which is converted by hydrogenolysis on Pd/C to trans-octahydrophenanthrene with D +46.6 deg (50percent ee).Similarly, intramolecular cyclization of 2-phenyl>-3,3-dimethyl-4(S)-methoxymethyl-5(S)-phenyloxazolidinium triflate produces, after hydrogenolysis on Pd/C, trans-octahydrophenanthrene with D -51.1 deg (55percent ee).The enantioselection in the cycloaddition with o-quinodimethane intermediate may be accounted for on the basis of ?-stacking interaction in the Diels-Alder transition state.
- Ito, Yoshihiko,Amino, Yusuke,Nakatsuka, Masashi,Saegusa, Takeo
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p. 1586 - 1590
(2007/10/02)
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- Resolution of N-acyl-DL (+)-phenylalanines
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The treatment of N-acyl-DL(+)-phenylalanines with D(-)-2-(2,5-dimethylbenzylamino)-1-butanol results in the formation of the D(-)-2-(2,5-dimethylbenzylamino)-1-butanol salt which is obtained as a crystallizate of the N-acyl-L(+)-phenylalanine and from which the desired N-acyl-L(+)-phenylalanine, an intermediate useful for the preparation of artificial sweetening agents, can be recovered.
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