N-protection of amino acid derivatives catalyzed by immobilized penicillin G acylase

The introduction of a N-α-phenylacetyl moiety into glycine, methionine and aspartic acid derivatives using immobilized penicillin G acylase (PGA) as catalyst was studied. High synthetic yields (86-97%) were obtained in biphasic systems under thermodynamic control using fully carboxy-protected derivatives of amino acids such as H-Gly-OMe, H-Gly-OBzl, H-Met-OEt, H-Asp(OBut)-OMe, H-Asp(OMe)-OMe and H-Asp(OBzl)-OBzl. Moderate yields (50-62%) were obtained for the N-α protection of β-carboxy free, α-carboxy esters of aspartic acid such as H-Asp-OMe and H-Asp-OBzl in methanol/buffer mixtures under kinetic control. The synthesis of some phenylacetyl derivatives on a preparative scale under the optimum conditions is also described. © 1997 OPA (Overseas Publishers Association) Amsterdam B. V. Published in The Netherlands by Harwood Academic Publishers.