The Experts below are selected from a list of 31896 Experts worldwide ranked by ideXlab platform
Sambasivarao Kotha - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of novel fluoranthene based conformationally constrained α Amino Acid Derivatives and polycyclic aromatics via the diels alder reaction
Synthesis, 2014Co-Authors: Sambasivarao Kotha, Milind MeshramAbstract:Conformationally constrained cyclic α-Amino Acid moieties have been fused to the fluoranthene system. Aminoindanecarboxylic Acid (Aic) and 1,2,3,4-tetrahydroisoquinolinecarboxylic Acid (Tic) Derivatives were synthesized by an alkylation sequence, whereas a Aminotetralincarboxylic Acid (Atc) derivative was assembled using the Diels–Alder reaction as a key step. These α-Amino Acid Derivatives are considered as constrained analogues of phenylalanine (Phe) and play an important role in the design and synthesis of bioactive peptides and some fluorescence chemosensor molecules. Moreover, this strategy has been extended to polycyclic aromatics via the Diels–Alder reaction and subsequent aromatization with DDQ.
-
the building block approach to unusual α Amino Acid Derivatives and peptides
Accounts of Chemical Research, 2003Co-Authors: Sambasivarao KothaAbstract:The building block approach was identified as a useful alternative to the commonly used Bucherer−Berg method for the preparation of cyclic unusual α-Amino Acid Derivatives. The symmetrical building blocks were prepared by dialkylation of ethyl isocyanoacetate under solid−liquid phase transfer catalysis conditions while the unsymmetrical building blocks were prepared by a stepwise alkylation of the O'Donnell Schiff base. Metathesis reactions, Suzuki couplings, and cycloaddition reactions were utilized to assemble the building blocks.
-
Modification of Indane-Based Unusual α-Amino Acid Derivatives via the Suzuki-Miyaura Coupling Reaction
Synthesis, 2002Co-Authors: Sambasivarao Kotha, Somnath Halder, Kakali LahiriAbstract:Various highly functionalized indane-based unusual α-Amino Acid Derivatives have been prepared via the Suzuki-Miyaura coupling reaction as a key step.
-
Diels-Alder approach to tetralin-based constrained α-Amino Acid Derivatives
Bioorganic & Medicinal Chemistry Letters, 2000Co-Authors: Sambasivarao Kotha, Thota Ganesh, Arun K. GhoshAbstract:Tetralin-based constrained α-Amino Acid Derivatives were prepared via [4+2]-cycloaddition reaction as a key step. Here sultine is used as a latent diene and 2-acetamidoacrylate serves as a dienophile component.
-
synthesis of indan based unusual α Amino Acid Derivatives under phase transfer catalysis conditions
Journal of Organic Chemistry, 2000Co-Authors: Sambasivarao Kotha, Enugurthi BrahmacharyAbstract:Conformationally constrained cyclic α-Amino Acid Derivatives were synthesized under solid-liquid phase-transfer catalysis conditions. This methodology involves the bis-alkylation of ethyl isocyanoacetate with various α,α‘-dibromo-o-xylene Derivatives [α,α‘-dibromo-o-xylene 5, 2,3-bis(bromomethyl)-1,4-dimethoxybenzene 6, 1,2-bis(bromomethyl)-4,5-dibromobenzene 7, 2,3-bis(bromomethyl)naphthalene 8, 1,8-bis(bromomethyl)-naphthalene 9, 6,7-bis(bromomethyl)-2,2-dimethyl-1H-phenalene-1,3(2H)-dione 10, 2,3-bis(bromomethyl)-1,4-anthraquinone 11, 6,7-bis(bromomethyl)quinoxaline 12, 3,4-bis(bromomethyl)furan 13, 1,2,4,5-tetrakis(bromomethyl)benzene 28, and hexakis(bromomethyl)benzene 30] using potassium carbonate as a base and tetrabutylammonium hydrogensulfate as a phase-transfer catalyst to give corresponding isonitrile Derivatives, which upon hydrolysis with HCl in ethanol gave Amino esters. Using this method electron-deficient as well as electron-rich and halogen-substituted indan-based α-Amino Acids were prepa...
Uttam K. Tambar - One of the best experts on this subject based on the ideXlab platform.
-
Stereoselective Synthesis of Functionalized Cyclic Amino Acid Derivatives via a [2,3]-Stevens Rearrangement and Ring-Closing Metathesis.
ChemInform, 2014Co-Authors: Aaron Nash, Arash Soheili, Uttam K. TambarAbstract:Unnatural cyclic Amino Acid Derivatives are accessible through a palladium-catalyzed tandem allylic amination/Stevens rearrangement followed by ring-closing metathesis.
-
Stereoselective synthesis of functionalized cyclic Amino Acid Derivatives via a [2,3]-Stevens rearrangement and ring-closing metathesis.
Organic letters, 2013Co-Authors: Aaron Nash, Arash Soheili, Uttam K. TambarAbstract:Unnatural cyclic Amino Acids are valuable tools in biomedical research and drug discovery. A two-step stereoselective strategy for converting simple glycine-derived Aminoesters into unnatural cyclic Amino Acid Derivatives has been developed. The process includes a palladium-catalyzed tandem allylic amination/[2,3]-Stevens rearrangement followed by a ruthenium-catalyzed ring-closing metathesis. The [2,3]-rearrangement proceeds with high diastereoselectivity through an exo transition state. Oppolzer’s chiral auxiliary was utilized to access an enantiopure cyclic Amino Acid by this approach, which will enable future biological applications.
Andrew D. Smith - One of the best experts on this subject based on the ideXlab platform.
-
tandem palladium and isothiourea relay catalysis enantioselective synthesis of α Amino Acid Derivatives via allylic amination and 2 3 sigmatropic rearrangement
Journal of the American Chemical Society, 2017Co-Authors: Stéphanie S. M. Spoehrle, Thomas H. West, James E. Taylor, Alexandra M. Z. Slawin, Andrew D. SmithAbstract:A tandem relay catalytic protocol using both Pd and isothiourea catalysis has been developed for the enantioselective synthesis of α-Amino Acid Derivatives containing two stereogenic centers from readily accessible N,N-disubstituted glycine aryl esters and allylic phosphates. The optimized process uses a bench-stable succinimide-based Pd precatalyst (FurCat) to promote Pd-catalyzed allylic ammonium salt generation from the allylic phosphate and the glycine aryl ester. Subsequent in situ enantioselective [2,3]-sigmatropic rearrangement catalyzed by the isothiourea benzotetramisole forms syn-α-Amino Acid Derivatives with high diastereo- and enantioselectivity. This methodology is most effective using 4-nitrophenylglycine esters and tolerates a variety of substituted cinnamic and styrenyl allylic ethyl phosphates. The use of challenging unsymmetrical N-allyl-N-methylglycine esters is also tolerated under the catalytic relay conditions without compromising stereoselectivity.
-
Tandem Palladium and Isothiourea Relay Catalysis: Enantioselective Synthesis of α‑Amino Acid Derivatives via Allylic Amination and [2,3]-Sigmatropic Rearrangement
2017Co-Authors: Stéphanie S. M. Spoehrle, Thomas H. West, James E. Taylor, Alexandra M. Z. Slawin, Andrew D. SmithAbstract:A tandem relay catalytic protocol using both Pd and isothiourea catalysis has been developed for the enantioselective synthesis of α-Amino Acid Derivatives containing two stereogenic centers from readily accessible N,N-disubstituted glycine aryl esters and allylic phosphates. The optimized process uses a bench-stable succinimide-based Pd precatalyst (FurCat) to promote Pd-catalyzed allylic ammonium salt generation from the allylic phosphate and the glycine aryl ester. Subsequent in situ enantioselective [2,3]-sigmatropic rearrangement catalyzed by the isothiourea benzotetramisole forms syn-α-Amino Acid Derivatives with high diastereo- and enantioselectivity. This methodology is most effective using 4-nitrophenylglycine esters and tolerates a variety of substituted cinnamic and styrenyl allylic ethyl phosphates. The use of challenging unsymmetrical N-allyl-N-methylglycine esters is also tolerated under the catalytic relay conditions without compromising stereoselectivity
Enugurthi Brahmachary - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of indan based unusual α Amino Acid Derivatives under phase transfer catalysis conditions
Journal of Organic Chemistry, 2000Co-Authors: Sambasivarao Kotha, Enugurthi BrahmacharyAbstract:Conformationally constrained cyclic α-Amino Acid Derivatives were synthesized under solid-liquid phase-transfer catalysis conditions. This methodology involves the bis-alkylation of ethyl isocyanoacetate with various α,α‘-dibromo-o-xylene Derivatives [α,α‘-dibromo-o-xylene 5, 2,3-bis(bromomethyl)-1,4-dimethoxybenzene 6, 1,2-bis(bromomethyl)-4,5-dibromobenzene 7, 2,3-bis(bromomethyl)naphthalene 8, 1,8-bis(bromomethyl)-naphthalene 9, 6,7-bis(bromomethyl)-2,2-dimethyl-1H-phenalene-1,3(2H)-dione 10, 2,3-bis(bromomethyl)-1,4-anthraquinone 11, 6,7-bis(bromomethyl)quinoxaline 12, 3,4-bis(bromomethyl)furan 13, 1,2,4,5-tetrakis(bromomethyl)benzene 28, and hexakis(bromomethyl)benzene 30] using potassium carbonate as a base and tetrabutylammonium hydrogensulfate as a phase-transfer catalyst to give corresponding isonitrile Derivatives, which upon hydrolysis with HCl in ethanol gave Amino esters. Using this method electron-deficient as well as electron-rich and halogen-substituted indan-based α-Amino Acids were prepa...
-
synthesis of conformationally constrained α Amino Acid Derivatives using ethyl isocyanoacetate as glycine equivalent
Bioorganic & Medicinal Chemistry Letters, 1997Co-Authors: Sambasivarao Kotha, Enugurthi BrahmacharyAbstract:Some novel cyclic α-Amino Acid Derivatives are prepared under solid-liquid phase-transfer catalytic conditions. Some of these Amino Acids prepared here are not directly accessible by the known methods.
Naresh Theddu - One of the best experts on this subject based on the ideXlab platform.
-
asymmetric synthesis of cyclic cis β Amino Acid Derivatives using sulfinimines and prochiral weinreb amide enolates
ChemInform, 2010Co-Authors: Franklin A Davis, Naresh ThedduAbstract:A new and highly stereoselective method to prepare 5-, 6-, and 7-membered cyclic cis-β-Amino Acid Derivatives is reported.
-
asymmetric synthesis of cyclic cis β Amino Acid Derivatives using sulfinimines and prochiral weinreb amide enolates
Journal of Organic Chemistry, 2010Co-Authors: Franklin A Davis, Naresh ThedduAbstract:Cyclic cis-β-Amino Weinreb amides, valuable building blocks for the asymmetric synthesis of cyclic β-Amino Acids Derivatives, are readily prepared via ring-closing metathesis of sulfinimine-derived N-sulfinyl β-Amino diene Weinreb amides. These unsaturated cyclic cis-β-Amino Weinreb amides are valuable building blocks for the asymmetric synthesis of cyclic β-Amino Acid Derivatives.