Repetitive Excess Mixed Anhydride (REMA) Synthesis of Peptides. The protected C‐terminal hexadecapeptide of secretin

The usefulness of the repetitive excess mixed anhydride (REMA) method of peptide synthesis was demonstrated by the prompt synthesis of the protected C‐terminal hexa‐decapeptide of the gastrointestinal hormone secretin, Boc‐Arg(NO 2 )‐Leu‐Arg(NO 2 )‐Asp(Bzl)‐Ser(Bzl)‐Ala‐Arg(NO 2 )‐Leu‐Gln‐Arg(NO 2 )‐Leu‐Leu‐Gln‐Gly‐Leu‐Val‐NH 2 ,(secretin 12–27). The overall yield was 31%, with an average coupling yield of 93%. Comparison of the physical constants of all intermediate sequcnces with those published, by Bodanszky et al. and by Wünsch et al. in their syntheses of secrctin, indicated identity. No significant raccmization could be detected in acid hydrolysates on digcstion with L ‐amino acid oxidase.