Peptide synthesis using novel S-sulfocysteine derivatives.

New cysteine S-sulfonate derivatives, Boc-Cys(SO3Na)-ONa 2 and Fmoc-Cys(SO3Na)-ONa 3, were prepared and their utility for peptide synthesis examined. The Fmoc derivative 3 was used in the solid-phase peptide synthesis of Arg8-vasopressin 9 via the Bunte salt 7. Satisfactory S-sulfonate stability was observed when p-cresol scavenged the cleavage from the resin.

[Immunodetermination of peptide factors. I. Synthesis of N-alpha-maleoyl-peptide derivatives].

A new synthesis of N-maleoyl-omega-amino acids, their use for the introduction of the maleimido group into peptide factors as well as the stability of this group under standard conditions of conventional peptide synthesis are described. The relatively high stability of N-maleoyl-peptide derivatives in aqueous solutions at neutral or slightly acidic pH values as well as the fast addition of thiol compounds to the maleimido group indicate that these peptide derivatives are well suited for the preparation of tracers of peptide factors and of peptide-protein conjugates.

Peptide sweeteners. 6. Structural studies on the C-terminal amino acid of L-aspartyl dipeptide sweeteners.

Stereochemical and structural aspects of the variations in the C-terminal residue of L-aspartyl-L-phenylalanine methyl ester have been investigated. Novel configurational analogues such as L-aspartyl-D-alanine benzyl ester and L-aspartyl-D-alpha-aminobutyric acid benzyl ester were found to be sweet. In addition, chiral and achiral alpha, alpha-dialkylglycine and alpha-aminocycloalkanecarboxylic acids were incorporated into the dipeptides.

[Syntheses of human little gastrin-I and its leucine-15, norleucine-15 and methoxinine-15 analogs].

Human little gastrin-I is known to exhibit a high tendency to air-oxidation of its methionine-15 residue to the corresponding S-oxide derivative, with concomitant loss of biological activity. Since its leucine-15 analog, even if fully biologically active, differs significantly from the parent hormone in the immunological properties, the norleucine-15 and methoxinine-15 analogues were synthetized. For the required comparative analyses new syntheses of human little gastrin-I and of its leucine-15 analog were additionally elaborated.