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Abstract

Polypeptide derivatives of the formula: a--x--b--y--c wherein x represents an acidic amino acid, preferably glu or asp, y represents a basic amino acid, preferably arg, lys or his, z represents hydrogen or a small protective group for the .alpha.-amino group in x, b represents a bond, a single amino acid or a peptide having up to 10 amino acids in the chain, and c represents --NR.sup.1 R.sup.2, wherein R.sup.1 and R.sup.2 are selected from the group consisting of hydrogen, C.sub.1 -C.sub.6 alkyl and C.sub.3 -C.sub.8 cycloalkyl, or R.sup.1 and R.sup.2 together with the attached nitrogen atom form a heterocyclic group optionally containing an additional hetero atom, or c represents --OR.sup.3, wherein R.sup.3 is selected from the group consisting of C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.8 cycloalkyl, benzyl, phenacyl, phthalimidomethyl, .beta.-methylthioethyl, 4-picolyl or substituted benzyl, or c is a single amino acid, except leu, or an amino acid derivative --z--d with the proviso that --z cannot be leu, and d may be --NR.sup.1 R.sup.2 or OR.sup.3, wherein R.sup.1, R.sup.2, and R.sup.3 are as defined above, or acid addition salts of such peptides, may be produced by peptide synthesis methods known per se. The polypeptides inhibit the glucose stimulated secretion of insulin from Langerhans's islets without affecting the secretion of glucagon, and potentiate the effect of insulin on the metabolism of glucose in isolated fat cells and in vivo potentiate the metabolism of glucose.

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First Claim