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A R West - One of the best experts on this subject based on the ideXlab platform.
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thermally induced homogeneous racemization polymorphism and crystallization of Pyroglutamic Acid
Crystal Growth & Design, 2011Co-Authors: A R WestAbstract:Pyroglutamic Acid (P) racemized spontaneously when heated above its melting temperature, ∼162 °C. No catalysts or solvents were involved in the racemization, and the rate was very temperature-dependent, requiring, for example, > 24.5 h at 160 °C but ∼1.5 h at 210 °C. The degree of racemization was studied indirectly by both X-ray powder diffraction and IR spectroscopy on samples that had been crystallized after melting for various times; the occurrence of racemization was also confirmed by HPLC analysis. The time spent in the molten state controlled the enantiomeric composition of the liquid and this had a major effect on the subsequent composition-dependent crystallization kinetics. Thus, crystallization of P from undercooled melt was particularly slow if the enantiomeric compositions of the melt and the crystallizing phases were significantly different; crystallization then required long-range counter-diffusion of P molecules in the viscous, hydrogen-bonded melt. On crystallization of P from melt, evide...
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polymorphism phase transitions and thermal stability of l Pyroglutamic Acid
Crystal Growth & Design, 2010Co-Authors: Nik Reevesmclaren, Jan Pokorny, Jack Yarwood, A R WestAbstract:l-Pyroglutamic Acid undergoes a phase transition, α → β, at ∼68 °C on heating, which is reversible with hysteresis depending on the cooling rate, before melting at ∼162 °C. On cooling, a further reversible transition, α → α′, which shows martensitic characteristics, occurs at ∼ −140 °C. The structural changes at the transitions were studied by variable temperature X-ray powder diffraction and Raman spectroscopy and compared with reports of single crystal structure determinations. Differences in Raman spectra were attributed to differences in intermolecular N−H···O interactions in the three enantiotropic polymorphs. By optical microscopy, crystals frequently jumped around the microscope slide on passing through the α/β transition; this is attributed to discontinuous changes in the unit cell dimensions leading to a spring effect in the crystals.
Mark G. Moloney - One of the best experts on this subject based on the ideXlab platform.
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Spirocyclic systems derived from Pyroglutamic Acid.
Organic & Biomolecular Chemistry, 2011Co-Authors: Andrew R. Cowley, Thomas J. Hill, Petr Kocis, Mark G. Moloney, Robert D. Stevenson, Amber L. ThompsonAbstract:The synthesis and likely conformational structure of rigid spirocyclic bislactams and lactam-lactones derived from Pyroglutamic Acid, and their suitability as lead structures for applications in drug development programmes using cheminformatic analysis, has been investgated.
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Stereocontrolled spirocyclic bislactams derived from Pyroglutamic Acid
Tetrahedron Letters, 2006Co-Authors: Thomas J. Hill, Petr Kocis, Mark G. MoloneyAbstract:The synthesis of rigid spirocyclic bislactams derived from Pyroglutamic Acid has been established.
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Stereoselective synthesis of conformationally constrained ω-amino Acid analogues from Pyroglutamic Acid
Organic & Biomolecular Chemistry, 2005Co-Authors: Emilie Bentz, Mark G. Moloney, Rajesh Goswami, Susan Marie WestawayAbstract:Bicyclic lactams derived from Pyroglutamic Acid provide a useful scaffold for synthesis of conformationally restricted analogues of lysine, ornithine and glutamine, as well as an Ala–Ala dipeptide analogue. Amino alcohol and carboxylic Acid derivatives are accessible from a common intermediate. In this strategy, the bicyclic lactam system not only controls, but also facilitates the determination of the stereochemistry of the synthetic intermediates.
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Pyrrolidinones derived from (S)-Pyroglutamic Acid. Part 2. Conformationally constrained kainoid analogues
Journal of the Chemical Society Perkin Transactions 1, 2000Co-Authors: James Dyer, Amanda King, Steve Keeling, Mark G. MoloneyAbstract:Novel conformationally constrained glutamate analogues are readily available from (S)-Pyroglutamic Acid using a bicyclic lactam as a synthetic template; diastereocontrolled modification of the pyrrolidine ring using a sequential conjugate addition–substitution strategy permits access to several kainoid analogues in a versatile strategy. The pyrrolidinone ring conformation appears to be controllable by the nature of remote substituents on the heterocyclic ring.
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Novel peptidomimetic structures: enantioselective synthesis of conformationally constrained lysine, ornithine and alanine analogues from Pyroglutamic Acid
Chemical Communications, 1999Co-Authors: Rajesh Goswami, Mark G. MoloneyAbstract:Conformationally constrained lysine and ornithine analogues, and an L-Ala-L-Ala dipeptide analogue, are available from Pyroglutamic Acid.
Benoît Rigo - One of the best experts on this subject based on the ideXlab platform.
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studies on pyrrolidinones reaction of Pyroglutamic Acid and vinylogues with aromatics in eaton s reagent
Tetrahedron, 2012Co-Authors: Alina Ghinet, Benoît Rigo, Nathalie Van Hijfte, Philippe Gautret, Hassan Oulyadi, Jolanta RousseauAbstract:Abstract The optimization of the synthesis of 5-aryl-2-pyrrolidinones through decarbonylation of Pyroglutamic Acid in Eaton’s reagent, in presence of aromatic derivatives, is described. The utilization of these reaction conditions in the arylation of enaminoester vinylogues (17, 24) of Pyroglutamic Acid was also realized, confirming that these derivatives are subject to decarbonylationi in the same way as the parent Acid. Depending on the nature of the aromatic derivative (15, 21, 28, and 32), two different families of compounds were obtained. Many by-products were also formed, suggesting a utilization of this reaction for compounds more stable than the enaminoesters and enaminonitriles used in this study. The possibility of enaminoesters reacting with aromatics in bimolecular reactions to give enaminoketones should also be noted. Five synthesized compounds were evaluated for their antiproliferative activity on the NCI-60 cancer cell lines panel.
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Studies on pyrrolidinones. Reaction of Pyroglutamic Acid and vinylogues with aromatics in Eaton’s reagent
Tetrahedron, 2012Co-Authors: Alina Ghinet, Benoît Rigo, Nathalie Van Hijfte, Philippe Gautret, Hassan Oulyadi, Jolanta RousseauAbstract:Abstract The optimization of the synthesis of 5-aryl-2-pyrrolidinones through decarbonylation of Pyroglutamic Acid in Eaton’s reagent, in presence of aromatic derivatives, is described. The utilization of these reaction conditions in the arylation of enaminoester vinylogues (17, 24) of Pyroglutamic Acid was also realized, confirming that these derivatives are subject to decarbonylationi in the same way as the parent Acid. Depending on the nature of the aromatic derivative (15, 21, 28, and 32), two different families of compounds were obtained. Many by-products were also formed, suggesting a utilization of this reaction for compounds more stable than the enaminoesters and enaminonitriles used in this study. The possibility of enaminoesters reacting with aromatics in bimolecular reactions to give enaminoketones should also be noted. Five synthesized compounds were evaluated for their antiproliferative activity on the NCI-60 cancer cell lines panel.
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studies on pyrrolidinones synthesis of 1 n acetylarylamino methyl Pyroglutamic Acid derivatives
Journal of Heterocyclic Chemistry, 1998Co-Authors: Samira El Ghammarti, Benoît Rigo, Hechmi Mejdi, Jean-pierre Hénichart, Daniel CouturierAbstract:Pyroglutamic Acid was transformed into 1-[(N-Acetylarylamino)methyl]Pyroglutamic Acid derivatives by using trimethylsilyl variations of the Mannich reaction.
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Studies on pyrrolidinones. Synthesis of 1‐[(N‐acetylarylamino)methyl]Pyroglutamic Acid derivatives
Journal of Heterocyclic Chemistry, 1998Co-Authors: Samira El Ghammarti, Benoît Rigo, Hechmi Mejdi, Jean-pierre Hénichart, Daniel CouturierAbstract:Pyroglutamic Acid was transformed into 1-[(N-Acetylarylamino)methyl]Pyroglutamic Acid derivatives by using trimethylsilyl variations of the Mannich reaction.
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On the cyclization of acyliminium salts derived from Pyroglutamic Acid
Tetrahedron Letters, 1996Co-Authors: Benoît Rigo, Samira El Ghammarti, Daniel CouturierAbstract:Abstract The Friedel Crafts reaction of Pyroglutamic Acid derivative 9 gives an acyliminium salt which cyclize to the condensed N-acylheterocycle 6 thus providing an easy access to the amine 1 .
Daniel Couturier - One of the best experts on this subject based on the ideXlab platform.
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studies on pyrrolidinones synthesis of 1 n acetylarylamino methyl Pyroglutamic Acid derivatives
Journal of Heterocyclic Chemistry, 1998Co-Authors: Samira El Ghammarti, Benoît Rigo, Hechmi Mejdi, Jean-pierre Hénichart, Daniel CouturierAbstract:Pyroglutamic Acid was transformed into 1-[(N-Acetylarylamino)methyl]Pyroglutamic Acid derivatives by using trimethylsilyl variations of the Mannich reaction.
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Studies on pyrrolidinones. Synthesis of 1‐[(N‐acetylarylamino)methyl]Pyroglutamic Acid derivatives
Journal of Heterocyclic Chemistry, 1998Co-Authors: Samira El Ghammarti, Benoît Rigo, Hechmi Mejdi, Jean-pierre Hénichart, Daniel CouturierAbstract:Pyroglutamic Acid was transformed into 1-[(N-Acetylarylamino)methyl]Pyroglutamic Acid derivatives by using trimethylsilyl variations of the Mannich reaction.
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On the cyclization of acyliminium salts derived from Pyroglutamic Acid
Tetrahedron Letters, 1996Co-Authors: Benoît Rigo, Samira El Ghammarti, Daniel CouturierAbstract:Abstract The Friedel Crafts reaction of Pyroglutamic Acid derivative 9 gives an acyliminium salt which cyclize to the condensed N-acylheterocycle 6 thus providing an easy access to the amine 1 .
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Studies on pyrrolidones. Synthesis and reactivity of β‐enaminomono‐esters and β‐enaminomononitriles derived from Pyroglutamic Acid
Journal of Heterocyclic Chemistry, 1994Co-Authors: D Fasseur, Benoît Rigo, Daniel Couturier, P Cauliez, Sebastien DefretinAbstract:In the Pyroglutamic Acid series, β-enaminoesters (3) were formed in the 2-position by opening of the corresponding Meldrum's derivative (6), and β-enaminonitriles (4) were obtained by treating carbamate vinylogous (5) by trimethylsilyl iodide. Alkylation and acylation of β-enaminoester (3a) was briefly examined
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studies on pyrrolidones synthesis and n alkylation of β enaminoesters derived from Pyroglutamic Acid
Journal of Heterocyclic Chemistry, 1992Co-Authors: D Fasseur, Benoît Rigo, Catherine Leduc, P Cauliez, Daniel CouturierAbstract:The condensation of iminoether 7, derived from Pyroglutamic Acid (4), with active methylene reagents such as Meldrum's Acid or methyl cyanoacetate, lead to β-enaminoesters 2. Solid-liquid phase transfer N-alkylation of these compounds is described.
Stuart L Schreiber - One of the best experts on this subject based on the ideXlab platform.
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stereospecific palladium catalyzed c h arylation of Pyroglutamic Acid derivatives at the c3 position enabled by 8 aminoquinoline as a directing group
Organic Letters, 2017Co-Authors: Oscar Verho, Micah Maetani, Bruno Melillo, Jochen Zoller, Stuart L SchreiberAbstract:An efficient and stereospecific Pd-catalyzed protocol for the C–H arylation of Pyroglutamic Acid derivatives that uses 8-aminoquinoline as a directing group is described. The reaction was shown to proceed efficiently with a variety of aryl and heteroaryl iodides bearing different functional groups, giving C3-arylated cis products in good to high yields. Removal of the 8-aminoquinoline unit from these C–H arylation products enables access to synthetically useful cis and trans Pyroglutamic Acid-based building blocks.
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Stereospecific Palladium-Catalyzed C–H Arylation of Pyroglutamic Acid Derivatives at the C3 Position Enabled by 8‑Aminoquinoline as a Directing Group
2017Co-Authors: Oscar Verho, Micah Maetani, Bruno Melillo, Jochen Zoller, Stuart L SchreiberAbstract:An efficient and stereospecific Pd-catalyzed protocol for the C–H arylation of Pyroglutamic Acid derivatives that uses 8-aminoquinoline as a directing group is described. The reaction was shown to proceed efficiently with a variety of aryl and heteroaryl iodides bearing different functional groups, giving C3-arylated cis products in good to high yields. Removal of the 8-aminoquinoline unit from these C–H arylation products enables access to synthetically useful cis and trans Pyroglutamic Acid-based building blocks
