Synthesis of enantiomerically enriched β-substituted analogs of (S)-α-alanine containing 1-phenyl-1H-1,2,3-triazole groups.

A synthesis of new enantiomerically enriched derivatives of (S)-α-aminopropionic acid, containing in the β-position 1,2,3-triazole groups coupled with a o-, m- and p-substituted phenyl residue, was developed based on Cu(I) catalyzed [3 + 2] cycloaddition of azides with alkynes. As the starting materials was used the square-planar Ni(II)complex of the Schiff base of propargylglycine with the chiral auxiliary BPB (Benzylprolylbenzophenone) and 1,4-substituted phenyl azides. The assignment of the (S)-absolute configuration of the α-carbon atom of the amino acid residue of the main diastereomeric complexes of the cycloaddition products was carried out on the basis of positive Cotton effects in the region of 480-580 nm of the circular dichroism spectra.

Synthesis, Characterization, and Study of Catalytic Activity of Chiral Cu(II) and Ni(II) Salen Complexes in the α-Amino Acid C-α Alkylation Reaction.

A new family of Cu(II) and Ni(II) salen complexes was synthesized and fully characterized through various physicochemical methods. Their catalytic activity was evaluated in the phase transfer C-alkylation reaction of the Schiff bases of D,L-alanine ester and benzaldehyde derivatives. It was found that the introduction of a chlorine atom into the - and -positions of the phenyl ring of the substrate resulted in an increase in both the chemical yield and the asymmetric induction ( 66-98%).

Sequential Heck Cross-Coupling and Hydrothiolation Reactions Taking Place in the Ligand Sphere of a Chiral Dehydroalanine Ni(II) Complex: Asymmetric Route to β-Aryl Substituted Cysteines.

A practically useful protocol for the asymmetric synthesis of artificial β-aryl-substituted cysteine derivatives was developed through sequential Pd(II)-catalyzed Heck cross-coupling with aryl iodides and hydrothiolation reaction with various alkyl thiols in the presence of triethylamine taking place in the ligand sphere of a robust and bench-stable chiral dehydroalanine Ni(II) complex. The subsequent acidic decomposition of the single diastereomeric Ni(II) complexes led to the target enantiopure cysteine derivatives.