Cyclic peptides. IX. Asymmetric hydrogenation of alpha, beta-dehydroamino acid residue in cyclodipeptides and preparation of optically pure alpha-amino acids.
A number of cyclo (delta aminoacyl-L-aminoacyl) (delta aminoacyl = delta Aba, delta Val, delta Leu, delta App, delta Phe and delta Trp; L-aminoacyl=L-Ala, L-Val, L-Leu and L-Lys (epsilon-Ac)) were synthesized by the condensation of cyclo (N-acetyl-Gly-N-acetyl-L-aminoacyl) with corresponding aldehyde or acetone and subsequent treatment with hydrazine. Each cyclo (delta aminoacyl-L-aminoacyl) except ones containing delta Phe and delta Trp was hydrogenated using Pd black in methanol to give cyclo (L-aminoacyl-L-aminoacyl) with high chiral induction. In the case of dehydro-cyclodipeptides containing delta Phe or delta Trp, slightly lower chiral induction was observed. Then, a mechanism of asymmetric hydrogenation was proposed. The influence of variation of solvent, temperature and catalyst on asymmetric hydrogenation was examined. Optically pure L-2-aminobutanoic acid, L-2-amino-5-phenylpentanoic acid and L-phenylalanine were synthesized on a preparative scale by this method and subsequent acid-hydrolysis.
D000096:Acetone; D000447:Aldehydes; D004151:Dipeptides / Q000138:chemical synthesis; D006834:Hydrazines; D007202:Indicators and Reagents; D008722:Methods; D010456:Peptides, Cyclic / Q000138:chemical synthesis*; D013329:Structure-Activity Relationship
D000447:Aldehydes; D004151:Dipeptides; D006834:Hydrazines; D007202:Indicators and Reagents; D010456:Peptides, Cyclic; D000096:Acetone