Preparative merits of the mixed anhydride (MA) method in the excess use of DDZ-amino acids in the peptide synthesis of biologically active new antamanide analogues.

The mixed anhydride (MA) method of peptide synthesis is further simplified by the repetitive excess use of Ddz-amino acids. In six comparative preparations of decapeptides this is demonstrated by the ease and speed of the synthetic manipulations, the efficiency of the monitoring of the reactions and purifications, and by the complete recycling of excess amino acid derivatives. In using of Ddz-amino acyl isobutylformate mixed anhydrides, side reactions are effectively suppressed, as proved by good coupling of Ddz-proline on to prolyl-peptides. Hydrophilic, crystalline and biological active antamanide analogues are obtained containg various functional side groups. The known cis-conformation of the antamanide prolyl-prolyl bonds is also established in the analogues by 13C-n.m.r. measurements. All new compounds are characterized by molecular peaks in the mass spectra.