Synthesis and properties of human β‐endorphin‐(1–9) and its analogs

Abstract

Four analogs of human β‐endorphin (βh‐EP) were synthesized by the solid‐phase method: βh‐EP‐(1–9) (I), [D‐Ala2]‐βh‐EP‐(1–9) (II), [Gln8]‐βh‐EP‐(1–9) (III), and [D‐Ala2, Gln8]‐βh‐EP‐(1–9) (IV). Measurement in a radioreceptor binding assay with use of tritiated βh‐EP as primary ligand gave relative potencies as follows: Met‐enkephalin, 100; I, 76; II, 100; III, 200; IV, 200. Two new amino acid derivatives were prepared and used for synthesis of the analogs: Nα‐t‐butyloxycarbonyl‐O‐(cyclopentyl) ‐tyrosine and Nα‐t‐butyloxycarbonyl‐γ‐(cyclopentyl)‐glutamic acid.

Solution‐Phase Peptide Synthesis

“…or 2-Adamantyl Ester, Asp(O-1-or 2-Ada) b-1or 2-Adamantylaspartate, Asp(O-1-Ada) 55 and Asp(O-2-Ada) 56 were synthesized[160,161]. The following protecting groups were reported: c-Benzylglutamate, Glu(OBzl) 57[162], c-tert-butylglutamate, Glu(OtBu) 58[149], c-cyclopentylglutamate, Glu(OcPe) 59[163], c-cyclohexylglutamate, Glu(OcHx) 60[160], c-cycloheptylglutamate, Glu(OcHp) 61[164], and c-2-adamantylglutamate Glu(O-2-Ada) 62[165]. Both groups are stable to 50% piperidine in dichloromethane (DCM).…”