Expedient synthesis of N-Z-pyroglutamyl-amino acid derivatives

N-Z-Pyroglutamyl pseudopeptides 3a–c are shown to be conveniently prepared from glutamyl-bis-Bt 1a by cyclization of an N-terminal glutamic acid residue. Structures are supported by 2D NMR studies and by comparison with the same products prepared by direct coupling of the C-terminus activated N-pGlu 1b and free amino acids 2a–c.