M. G. Ryzhov

Bio: M. G. Ryzhov is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Amino acid & Enantioselective synthesis. The author has an hindex of 3, co-authored 5 publications receiving 264 citations.

General method of diastereo- and enantioselective synthesis of β-hydroxy-α-amino acids by condensation of aldehydes and ketones with glycine

Abstract: Synthese en particulier de serine, hydroxy-3 valine, hydroxy-2 phenylserine, phenylserine et methylenedioxy-3,4 phenylserine

General method of diastereo- and enantioselective synthesis of β-hydroxy-α-amino acids by condensation of aldehydes and ketones with glycine

Abstract: Synthese en particulier de serine, hydroxy-3 valine, hydroxy-2 phenylserine, phenylserine et methylenedioxy-3,4 phenylserine

Asymmetric synthesis of threonine and retroracemization of amino acids using Ni(II) complexes of Schiff bases with S-2-n-(N′-benzylprolyl)aminobenzaldehyde

Abstract: 1. Complexes of Ni(II) with Schiff bases of 2-N-(2′-S-N-benzylpyrrolidin-2-carbonyl)aminobenzaldehyde (S-BPaB) with glycine and valine have been synthesized in which the Ni ion is coordinated with the N atoms of the proline fragment, of the aldimine group, of the ionized amide, and with the carboxyl group. 2. The presence has been shown of enantioselective effects in complexes of Schiff bases of S-BPAB with R,S-amino acids with Ni(II) which increase with an increase in volume of the amino acid side chain. The enantiomer excess for the complex with S-Val was 78%. 3. The retroracemization of alanine, valine, norvaline, phenylalanine, phenylglycine, and tryptophan was carried out using S-BPAB and Ni(II) with enantiomer yields of 15, 78, 42, 40, 39, and 64% respectively. 4. The asymmetric synthesis of S-threonine has been effected by condensing acetaldehyde with (S-BPAB-Gly)·Ni(II) on catalysis with Et3N with a S-Thr and S-allo-Thr ratio of 1∶2 and enantiomer yield of 86 and 76% respectively. An increase in pH led to a reduction in enantiomer yield and reversal of the sign of the enantioselective effect. 5. A method has been developed for enantiomer analysis of tryptophan using high-pressure liquid chromatography as has a GLC method for difficult amino acids using a high-temperature chiral chromatographic phase, viz., N-heptadecanoyl-S-Val tert-butylamide.

Addition of chiral glycine, methionine, and vinylglycine enolate derivatives to aldehydes and ketones in the preparation of enantiomerically pure α-amino-β-hydroxy acids

Abstract: Chiral enolates of imidazolidinones and oxazolidinones from the title amino acids react with carbonyl compounds to afford the corresponding alcohols in excellent yields (see Scheme 5). Furthermore, the addition to aldehydes proceeds with high diastereoselectivity to give, after acid hydrolysis, threo-α-amino-β-hydroxy acids of high enantiomeric purity. Some of the threo-α-amino-β-hydroxy acids prepared in this work are the proteinogenic (S)-threonine (26), the naturally occurring (S)-3-phenylserine (28), and (S)-3-hydroxyleucine (27) as well as the unnatural (S)-4,4,4-trifluorothreonine (30) and (S)-3-(4-pyridyl)serine (31). The N-methylamide of (2S,3R,4R,6E)-3-hydroxy-4-methyl-2-(methylamino)-6-octenoic acid (32), the unique amino acid in the immunosuppressive cyclosporine, was prepared by the new method. This report presents also information suggesting that both steric and stereoelectronic effects are responsible for the good stereoselectivities observed.

Approaches to Obtaining Fluorinated α-Amino Acids.

Abstract: Fluorine does not belong to the pool of chemical elements that nature uses to build organic matter. However, chemists have exploited the unique properties of fluorine and produced countless fluoro-organic compounds without which our everyday lives would be unimaginable. The incorporation of fluorine into amino acids established a completely new class of amino acids and their properties, and those of the biopolymers constructed from them are extremely interesting. Increasing interest in this class of amino acids caused the demand for robust and stereoselective synthetic protocols that enable straightforward access to these building blocks. Herein, we present a comprehensive account of the literature in this field going back to 1995. We place special emphasis on a particular fluorination strategy. The four main sections describe fluorinated versions of alkyl, cyclic, aromatic amino acids, and also nickel-complexes to access them. We progress by one carbon unit increments. Special cases of amino acids for which there is no natural counterpart are described at the end of each section. Synthetic access to each of the amino acids is summarized in form of a table at the end of this article with the aim to make the information easily accessible to the reader.