28385-45-7Relevant academic research and scientific papers
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 (2017)
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.
Synthesis of quaternary α-methyl α-amino acids by asymmetric alkylation of pseudoephenamine alaninamide pivaldimine
Hugelshofer, Cedric L.,Mellem, Kevin T.,Myers, Andrew G.
supporting information, p. 3134 - 3137 (2013/07/26)
The utility of pseudoephenamine as a chiral auxiliary for the alkylative construction of quaternary α-methyl α-amino acids is demonstrated. The method is notable for the high diastereoselectivities of the alkylation reactions, for its versatility with respect to electrophilic substrate partners, and for its mild hydrolysis conditions, which provide α-amino acids without salt contaminants. Alternatively, α-amino esters can be obtained by direct alcoholysis.
Chiral salen ligands designed to form polymetallic complexes
Achard, Thierry R.J.,Clegg, William,Harrington, Ross W.,North, Michael
experimental part, p. 133 - 144 (2012/01/06)
Chiral salen ligands capable of forming polymetallic complexes have been designed. The ligands possess substituents in the 4,4′-positions, but have no substituent in the 3,3′-positions to allow a second metal ion access to the salen oxygen atoms. Ligands in which a polyether chain links the 4,4′-positions were prepared and complexed to copper. In addition, acyclic ligands with potential metal coordinating substituents in the 4,4′-positions were prepared and complexed to copper and cobalt. The crystal structure of one of the cobalt complexes shows it to be a trimetallic complex in which a Co(II)(OAc)2 group coordinates to the salen oxygen atoms of two Co(III)(salen)(OAc) units. In contrast, the crystal structure of a Co(salen) complex with tert-butyl groups attached to the 3,3′-positions is found to be mononuclear. All of the complexes were tested as asymmetric phase transfer catalysts for the asymmetric alkylation of an alanine methyl ester, forming (R)-α-methyl phenylalanine methyl ester with up to 85% ee.
A pictet-spengler cyclisation methodology for the construction of nonproteinogenic tetrahydroisoquinoline quaternary amino acids
Page, Philip C. Bulman,Parkes, Genna A.,Buckley, Benjamin R.,Wailes, J. Steven
, p. 3005 - 3007 (2012/01/05)
A simple highly stereoselective route to tetrahydroisoquinoline quaternary amino acids from phenylalanine is described. Georg Thieme Verlag Stuttgart · New York.
Enantioselective synthesis of -benzylalanine using trans -3,4-Dihydro-3,4-diaryldibenzo[ c, g ]phenanthrene-3,4-diols
Kitamura, Mitsuru,Kitahara, Daisuke,Okauchi, Tatsuo
body text, p. 2097 - 2100 (2010/10/21)
Asymmetric benzylation of a benzophenone Schiffs base of alanine ethyl ester was successfully conducted using trans-3,4-dihydro-3,4-diaryldibenzo[c,g] phenanthrene-3,4-diol as a chiral source.
Asymmetric catalysis of carbon-carbon bond forming reactions using amino acid-derived C1-symmetrical salen ligands
Belokon, Yuri N.,Hunt, Jamie,North, Michael
experimental part, p. 2804 - 2815 (2009/06/28)
Four amino acids (alanine, valine, phenylalanine and phenylglycine) have been converted into C1-symmetrical salen ligands and complexed to titanium, vanadium, copper and cobalt. The resulting complexes have been used as asymmetric catalysts for asymmetric cyanohydrin synthesis, asymmetric Strecker reactions, asymmetric synthesis of α-methyl amino acids and asymmetric Darzens condensations. Satisfactory levels of asymmetric induction were obtained from reactions in which the (salen)metal complex acts as a chiral Lewis acid, but low levels of asymmetric induction were obtained from reactions carried out under solid-liquid phase-transfer conditions.
Enantioselective [1,2]-Stevens rearrangement using sugar-derived alkoxides as chiral promoters
Tomooka, Katsuhiko,Sakamaki, Junichiro,Harada, Manabu,Wada, Ryoji
, p. 683 - 686 (2008/12/20)
The first example of enantioselective base-induced [1,2]-Stevens rearrangement was achieved by using the newly developed D-glucose-derived lithium alkoxide as a chiral promoter. This rearrangement provides an α-amino ketone having a pseudoquaternary chira
Diastereoselective synthesis of quaternary α-amino acids from diketopiperazine templates
Davies, Stephen G.,Christopher Garner,Ouzman, Jaqueline V. A.,Roberts, Paul M.,Smith, Andrew D.,Snow, Emma J.,Thomson, James E.,Tamayo, Juan A.,Vickers, Richard J.
, p. 2138 - 2147 (2008/03/14)
Sequential enolate alkylations of (S)-N(1)-methyl-5-methoxy-6-isopropyl-3, 6-dihydropyrazin-2-one and (S)-N(1)-p-methoxybenzyl-5-methoxy-6-isopropyl-3,6- dihydropyrazin-2-one proceed with excellent levels of diastereoselectivity (>90% de) affording quaternary α-amino acids in high enantiomeric excess (>98% ee) after deprotection and hydrolysis. This journal is The Royal Society of Chemistry.
Enantiocontrolled synthesis of α-methyl amino acids via Bn 2N-α-methylserine-β-lactone
Smith, Nicole D.,Wohlrab, Aaron M.,Goodman, Murray
, p. 255 - 258 (2007/10/03)
(Chemical Equation Presented) Enantiocontrolled synthesis of α-methyl amino acids proceeds via the regioselective organocuprate opening of Bn 2N-α-methylserine-β-lactone. From this chiral intermediate, a wide variety of α-methyl amino acids and
Influence of the metal and chiral diamine on metal(II)salen catalysed, asymmetric synthesis of α-methyl α-amino acids
Belokon, Yuri N.,Fuentes, Jose,North, Michael,Steed, Jonathan W.
, p. 3191 - 3204 (2007/10/03)
The influence of the metal ion and chiral diamine used to form a metal(salen) complex on the catalytic activity of the complex in the asymmetric benzylation of an alanine enolate was investigated. Only metal ions which could form square-planar complexes g
