Showing papers by "Vadim A. Soloshonok published in 1993"

General method for the synthesis of enantiomerically pure β-hydroxy-α-amino acids, containing fluorine atoms in the side chains. Case of stereochemical distinction between methyl and trifluoromethyl groups. X-Ray crystal and molecular structure of the nickel(II) complex of (2S,3S)-2(trifluoromethyl)threonine

Abstract: The chiral NiII complex 1 of a Schiff's base derived from (S)-o-[N-(N-benzylprolyl)amino] benzophenone (BPB) and glycine was treated with fluoro-substituted aldehydes (aliphatic and aromatic)in MeOH or CHCl3. The addition proceeds with high diastereoselectivity to give, if catalysed by MeONa in MeOH, the corresponding complexes of syn-(2R)-3-fluorophenylserines (84–100% d.e.) and syn-(2S)-fluoroalkylserines (90% d.e.), and, if catalysed by NEt3 or DABCO (MeOH or CHCl3), the corresponding complexes of syn-(2S)-, and anti-(2S)-3-fluorophenylserines and fluoroalkylserines. The second-order asymmetric transformation may be successfully employed to obtain diastereoisomerically pure complexes of anti-(2R)-3-fluorophenylserines. Condensation of trifluoroacetone with complex 1, catalysed by MeONa, gave predominantly (at least >95% d.e.) the diastereoisomeric complex, containing (2S,3S)-β-(trifluoromethyl)threonine, as shown by an X-ray diffraction structural study. Diastereoisomerically and enantiomerically pure fluorine-containing 3-phenyl- and 3-alkyl-serines were obtained from the corresponding diastereoisomerically pure complexes, separated by chromatography or crystallization. The initial chiral auxiliary BPS was recovered (80–98%). The influence of the reaction's conditions and the nature of the corresponding fluoro-substituted aldehydes on the diastereoselectivity of the reactions is discussed.

Asymmetric Synthesis of Organoelement Analogues of Natural Products; Part 12: General Method for the Asymmetric Synthesis of Fluorine-Containing Phenylalanines and α-Methyl(phenyl)alanines via Alkylation of the Chiral Nickel(II) Schiff's Base Complexes of Glycine and Alanine

Abstract: Nickel(II) complexes of Schiffs bases derived from (S)-o-[(N-benzyl]prolyl)amino]benzophenone [N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide] (BBP) and glycine or alanine have been used for asymmetric synthesis of fluoro (S)-phenylalanines and (S)-α-methyl(phenyl)alanines. Large selectivity (>90%) is observed for the alkylation of both complexes.

Asymmetric synthesis of fluorine- and phosphorus-containing analogues of aminoacids

Abstract: The available literature data on the methods for the asymmetric synthesis of fluorine- and phosphorus-containing aminoacids are surveyed. The chemical and enzymic methods of the asymmetric synthesis of the above compounds are considered. The bibliography includes 139 references.

Asymmetric synthesis of organoelement analogs of natural products

Abstract: Michael addition of octafluoropentyl vinylsulfonate to complexes of Ni(II) with Schiffs bases derived from 5-2-N-(N-benzylprolyl)-o-aminobenzophenone and glycine orS-2-N-(N-benzylprolyl)-o-aminobenzaldehyde and alanine is a convenient preparative method for asymmetric synthesis of previously unknown fluorinated esters ofS-homocysteic acid.

Transamination of Fluorinated β-Keto Carboxylic Esters. A Biomimetic Approach to β-Polyfluoroalkyl β-Amino Acids.

Abstract: The base-catalyzed isomerization of N-benzylimines (or enamines) of β-polyfluoroalkyl-β-ketocarboxylic esters cleanly affords the N-benzylidene derivatives of β-polyfluoro-β-aminocarboxylic esters which are hydrolyzed to corresponding amino acids in high overall yields.