Studies on the enantioselective synthesis of α-amino acids via asymmetric phase-transfer catalysis

Preparation and Characterization of [5‐13C]‐(2S,4R)‐Leucine and [4‐13C]‐(2S,3S)‐Valine − Establishing Synthetic Schemes to Prepare Any Site‐Directed Isotopomer of L‐Leucine, L‐Isoleucine and L‐Valine

“…Recently, the asymmetric alkylation of tert-butyl N-(diphenylmethylene)glycinate (26) under cinchona alkaloid derived phase-transfer catalytic conditions has been optimized. [21,26] The reaction conditions are mild with a high yield of α-amino acids and very high enantiomeric excess. Additional advantages of this method are that 4668 the base, the chiral catalyst and the tert-butyl N-(diphenylmethylene)glycinate (26) are all commercially available.…”

“…[21,26] The reaction conditions are mild with a high yield of α-amino acids and very high enantiomeric excess. Additional advantages of this method are that 4668 the base, the chiral catalyst and the tert-butyl N-(diphenylmethylene)glycinate (26) are all commercially available. In order to test the procedure we treated commercial 2-methylpropyl iodide with the protected glycine ester 22.…”

Nucleophilic addition to an achiral dehydroalanine Schiff base Ni(II) complex as a route to amino acids. A case of stereodetermining asymmetric protonation in the presence of TADDOL

“…Any substitution of OH groups in TADDOL 7a by Cl-, SH-, NHCOCF 3 or NH 2 -groups invariably decreased the enantioselectivity of the process (Table 3, run 1-6). Changing the substitutes on TADDOL from ketal (R 1, R 2 ≠ H) to acetal (R 2 = H) also influenced the outcome of the reaction.…”

“…2 It is generally assumed that the stereoselective formation of the C-C bonds and consequently of the amino acid occur at the stage of the addition of the intermediate enolate of the glycine derivative to the activated C=C bond of acrylic derivatives within the ion pair formed by Cinchona alkaloid ammonium salt and the enolate. 3 Another possibility of introducing asymmetry into the adduct by enantioselective catalytic protonation of the intermediate enolate was generally neglected. To the best of our knowledge only a few papers have been published on the subject of asymmetric catalytic C-H bond formation without a preceding enantioselective C-C-bond-forming step in the Michael addition.…”

Using the same organocatalyst for asymmetric synthesis of both enantiomers of glutamic acid-derived Ni(II) complexes via 1,4-additions of achiral glycine and dehydroalanine Schiff base Ni(II) complexes

“…This was a reason why the methods of asymmetric synthesis of Glu and its derivatives were sought. Presently, several synthetic protocols have been elaborated based on both stoichiometric (Williams 1989;Duthaler 1994;Cativiela and de DÍaz Villegas 1998;Ma 2003) and catalytic versions (Maruoka and Ooi 2003;Corey et al 1998;Vyskočil et al 2002;Belokon et al 2003;Lygo et al 2001;Nájera and Sansano 2007;Tsubogo et al 2010;Kobayashi and Electronic supplementary material The online version of this article (doi:10.1007/s00726-011-1076-y) contains supplementary material, which is available to authorized users. Yamashita 2011) of Michael additions of chiral or achiral activated Gly derivatives to acrylic acid derivatives.…”