88820-87-5Relevant articles and documents
Quaternized α,α′-Amino Acids via Curtius Rearrangement of Substituted Malonate-Imidazolidinones
Gokada, Maheswara Rao,Hunter, Roger,Andrijevic, Ana,Petersen, Wade F.,Samanta, Sauvik,Venter, Gerhard,Rees-Jones, Sophie
, p. 10650 - 10658 (2018/05/31)
An efficient synthesis protocol is presented for accessing quaternized α-amino acids in chiral, nonracemic form via diastereoselective malonate alkylation followed by C- to N-transposition. The key stereodifferentiating step involves a diastereoselective alkylation of an α-monosubstituted malonate-imidazolidinone, which is followed first by a chemoselective malonate PMB ester removal and then a Curtius rearrangement to provide the transposition. The method demonstrates a high product ee (89-99% for eight cases) for quaternizing a range of proteinogenic α-amino acids. The stereogenicity in targets 5a-i supports previous conclusions that the diastereoselective alkylation step proceeds via an α-substituted malonate-imidazolidinone enolate in its Z-configuration, with the auxiliary in an s-transC-N conformation.
A cross-metathesis route to functionalized α-methyl α-substituted amino acids
Storcken, Roy P. M.,Panella, Lavinia,Van Delft, Floris L.,Kaptein, Bernard,Broxterman, Quirinus B.,Schoemaker, Hans E.,Rutjes, Floris P. J. T.
, p. 161 - 164 (2008/02/03)
A chemoenzymatic approach to the synthesis of functionalized α-methyl α-substituted amino acids is detailed. This involves amidasemediated enzymatic resolution of α-methyl α-substituted side-chain ω-unsaturated amino acids followed by functionalization via cross-metathesis.
Enantioselective syntheses of aeruginosin 298-A and its analogues using a catalytic asymmetric phase-transfer reaction and epoxidation
Ohshima, Takashi,Gnanadesikan, Vijay,Shibuguchi, Tomoyuki,Fukuta, Yuhei,Nemoto, Tetsuhiro,Shibasaki, Masakatsu
, p. 11206 - 11207 (2007/10/03)
We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic part, and counteranion). Copyright
A practical asymmetric synthesis of α-methyl α-amino acids using a chiral cu-salen complex as a phase transfer catalyst
Belokon',Davies,North
, p. 7245 - 7248 (2007/10/03)
The asymmetric C-alkylation of N-benzylidene alanine methyl ester has been achieved using a copper(II) (salen) complex as an asymmetric phase transfer catalyst and provides a practical synthesis of α-methyl α-amino acids with up to 86% enantiomeric excess. (C) 2000 Elsevier Science Ltd.
Synthesis of enantiopure functionalized pipecolic acids via amino acid derived N-acyliminium ions
Rutjes, Floris P. J. T.,Veerman, Johan J. N.,Meester, Wim J. N.,Hiemstra, Henk,Schoemaker, Hans E.
, p. 1127 - 1135 (2007/10/03)
The synthesis and enzymatic resolution of a novel vinylsilane-containing amino acid is described. Derivatization of this and other olefinic amino acids followed by subjection to standard N-acyliminium ion cyclization conditions provides the corresponding pipecolic acid derivatives with - in most cases - complete conservation of enantiopurity. In addition to studying the scope of this reaction, details of the N-acyliminium ion cyclization including an aza Cope equilibrium are highlighted.
Ruthenium-catalyzed ring closing olefin metathesis of non-natural α-amino acids
Rutjes, Floris P. J. T.,Schoemaker, Hans E.
, p. 677 - 680 (2007/10/03)
The use of various enantiopure amino acid-derived diolefins as substrates for the ring closing olefin metathesis reaction (RCM) has been investigated. This reaction has been shown to be an efficient transformation for providing highly functionalized 6- and 7-membered ring amino acids.
Synthesis of (Optically Active) Sulfur-Containing Trifunctional Amino Acids by Radical Addition to (Optically Active) Unsaturated Amino Acids
Broxterman, Quirinus B.,Kaptein, Bernard,Kamphuis, Johan,Schoemaker, Hans E.
, p. 6286 - 6294 (2007/10/02)
Sulfur-based radicals, generated from R-S-H-type precursors (R = alkyl, acyl) with AIBN, smoothly add to α-allylglycines protected at none, one, or both of the amino acid functions (NH2 and/or CO2H).Sulfur-containing trifunctional amino acids were obtained in good to excellent yields (64-100 percent).The solvent used for the reaction is critical.Optimal results were obtained when both the unsaturated amino acid and RSH dissolve completely in the medium (dioxane/water or methanol/water are good solvent systems).The scope of the reaction includes α-substituted α-allylglycine derivative and derivatives as well as β-substituted β-allyl-β-amino alcohols.In the case of optically active α-allylglycine derivatives, radical addition is accompanied by a small amount of racemization, the amount depending on the type of protection and R-S-H.The products are easily optically enriched by crystallization.Addition of sulfur-based radicals to α-allylglycine is believed to be an example of a general method for synthesizing optically active trifunctional amino acids from unsaturated amino acids.
ALKYLATION AND PROTONATION OF CHIRAL SCHIFF BASES: DIASTEREOSELECTIVITY AS A FUNCTION OF THE NATURE OF REACTANTS
Tabcheh, Mohamed,Achqar, Abdelrhani El,Pappalardo, Louis,Roumestant, Marie-Louise,Viallefont, Philippe
, p. 4611 - 4618 (2007/10/02)
The factors controlling the diastereoselective alkylation and protonation reactions of chiral Schiff bases prepared from 2-hydroxypinan-3-one and α-aminoesters are reported: nature of the ester, of the alkylating agent and of the base.
Asymmetric Syntheses via Heterocyclic Intermediates, V. - Asymmetric Synthesis of α-Methyl Amino Acids by Alkylation of the Lithiated Lactim Ether of cyclo-(L-Ala-L-Ala)
Schoellkopf, Ulrich,Hartwig, Wolfgang,Groth, Ulrich,Westphalen, Karl-Otto
, p. 696 - 708 (2007/10/02)
The (3S,6S)-2,5-dimethoxy-3,6-dimethyl-3,6-dihydropyrazine (7) is obtained from cyclo-(L-Ala-L-Ala) 5 (93-95percent optically pure) and trimethyloxonium tetrafluoroborate.With butyllithium the lithio derivative 8 is formed which reacts with alkyl halides in good chemical yields and with more than 90percent diastereoselectivity, whereby R-configuration is induced at C-3.A model concept is discussed, which explains the remarkably high asymmetric induction. - Hydrolysis (0.25 N HCl, room temp.) gives L-alanine methyl ester (4) and the (R)-α-methyl amino acid methyl esters 13.The two amino acid esters are separable by distillation or chromatography.
