Showing papers by "Vadim A. Soloshonok published in 2008"

Efficient asymmetric synthesis of the functionalized pyroglutamate core unit common to oxazolomycin and neooxazolomycin using Michael reaction of nucleophilic glycine Schiff base with α,β-disubstituted acrylate

Abstract: The functionalized pyroglutamate core unit, (2R,4R)-3, which could be converted into the β-lactone/pyrrolidine or γ-lactone/pyrrolidine ring system of oxazolomycin A 1 and neooxazolomycin 2, and which possesses an exomethylene group at C3 as a scaffold for the construction of their C3 polyene segment, was synthesized by the Michael reaction of a glycine Schiff base 4 with the α,β-disubstituted acrylate 8 as the key step.

Asymmetric Synthesis of (2S,3S)- and(2R,3R)-α,β-Dialkyl-α-aminoAcids via Alkylation of Chiral Nickel(II) Complexes of Aliphatic α-AminoAcids with Racemic α-Alkylbenzyl Bromides

Abstract: This studv has demonstrated that the stereochemical outcome of the direct alkylation of nickel(II) complexes derived from chiral Schiff bases of glycine, alanine, 2-aminobutyric acid, and leucine with racemic α-methylbenzyl bromide depends on the steric bulk of the corresponding amino acid residue. In particular, the alkylation of the alanine complex was found to proceed with a synthetically useful level (90% de) of stereoselectivity offering a concise synthesis of enantiomerically pure (2S,3S)- or (2R,3R)-α,β-dimethylphenylalanines.

Efficient and Practical Protection of the Catechol Residue of 3,4-Dihydroxyphenylalanine (DOPA) Derivative as Acetonide

Abstract: The acetonide formation of 3,4 -dihydroxyphenylalanine (DOPA) derivative was realized under efficient and practical reaction conditions: the reaction of the methyl ester of DOPA in ace-tone-i-PrOH in the presence of 5 mol% of TsOH afforded the catechol side chain protected DOPA as an acetonide in quantitative yield; the workup procedure is a simple evaporation of the solvents. This methodology allows an access to the reaction in large scale.