A general asymmetric synthesis of artificial aliphatic and perfluoroalkylated α-amino acids by Luche's cross-electrophile coupling reaction

A synthetic route to artificial chiral α-amino acids featuring a 3,4-dihydroisoquinolone core through a Rh(III)-catalyzed functionalization of allyl groups in chiral Ni(II) complexes

Currently, non-proteinogenic α-amino acids (α-AAs) have attracted increasing interest in bio- and medicinal chemistry. In this context, the first protocol for the asymmetric synthesis of artificial α-AAs featuring a 3,4-dihydroisoquinolone core with two stereogenic centers was successfully elaborated. A straightforward Rh(III)-catalysed C-H activation/annulation reaction of various aryl hydroxamates with a set of robust and readily available chiral Ni(II) complexes, which have allylic appendages derived from glycine (Gly), alanine (Ala) and phenylalanine (Phe), allowed incorporation of a 3,4-dihydroisoquinolone scaffold into the chiral amino acid residue. The reaction was performed in methanol and under mild conditions (at room temperature under air atmosphere), providing separable diastereomeric complexes with up to 94% total yield. The target α-AA with a 3,4-dihydroisoquinolone core in an enantiopure form was subsequently released from the obtained chiral Ni(II) complexes via an acidic decomposition in aqueous HCl, along with the recovery of the chiral auxiliary ligand.

An asymmetric metal-templated route to amino acids with an isoquinolone core via a Rh(III)-catalyzed coupling of aryl hydroxamates with chiral propargylglycine Ni(II) complexes

A general protocol for the asymmetric synthesis of artificial amino acids (AAs) comprising an isoquinolone skeleton was successfully elaborated via a straightforward Rh(III)-catalyzed C-H activation/annulation of various aryl hydroxamates with a series of robust chiral propargylglycine Ni(II) complexes derived from glycine (Gly), alanine (Ala) and phenylalanine (Phe) in a green solvent (methanol) under mild conditions (at room temperature under air). Notably, in the case of phenylalanine-derived complexes, the formation of unfavorable 4-substituted isoquinolone regioisomers was achieved by a catalyst control for the first time. The subsequent acidic decomposition of the obtained Ni(II) complexes provides the target unnatural α- and α,α-disubstituted AAs with an isoquinolone core in an enantiopure form.

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.