Abstract: Renin inhibitory peptides of the formula ##STR1## and analogs thereof inhibit renin and are useful for treating various forms of renin-associated hypertension and hyperaldosteronism.

Abstract: Monoiodinated-tyrosine derivatives of synthetic fragments of mammalian atrial natriuretic factor are biologically active and are useful to determine the mode of biological activity and the effect of derivatization on biological activity.

Abstract: Synthetic novel cyclic hexapeptides having the structure:Cyclo[(N-alkylamino acid)-X-(N-alkylamino acid)'-X-(N-alkylamino acid)"-X]wherein (N-alkylamino acid), (N-alkylamino acid)' and (N-alkylamino acid)" have the structure: ##STR1## wherein R.sup.1 is a lower alkyl group having 1 to 3 carbon atoms and R.sup.2 is hydrogen and methyl or R.sup.1 and R.sup.2 are --CH.sub.2 --N, n being an integer 2 or 3, and form a 4- or 5- membered ring; and X is D- or L-Ala, D- or L-Phe, D- or L-Leu, D- or L-p-halophenylalanyl or D- or L-p-nitrophenylalanyl, with the proviso that when R.sup.1 is methyl and R.sup.2 is hydrogen, X is not D-Ala are prepared. Oral administration of these cyclic peptides improves the digestive efficiency of certain herbivorous animals.

Abstract: Synthetic antigens related to luteinizing hormone-releasing hormone (hereinafter designated LH-RH) having the amino acid composition, pyroglutamyl-histidyl-tryptophanylseryl-tyrosyl-glycyl-leucyl-arginyl-prol yl-glycyl-poly-L-lysine (hereinafter designated pyroglu-his-trp-ser-tyr-glyleu-arg-pro-gly-poly-L-lys) and poly-L-lysyl-glutarylhistidyl-tryptophanyl-seryl-tyrosyl-glycyl-leucyl-arg inylprolyl-glycine amide (hereinafter designated poly-L-lysglutaryl-his-trp-ser-tyr-gly-leu-arg-pro-gly) are prepared by coupling the corresponding decapeptide with poly-L-lysine. The corresponding decapeptides are prepared by controlled stepwise procedures starting with individual amino acid components. These antigens have the property of inducing formation of antibodies to luteinizing hormone-releasing hormone (LH-RH) in animals.

Abstract: Novel N-protected-.alpha.-amino acid compounds are disclosed in which the amino functionality is protected by a 1-methylcyclobutyloxycarbonyl or 1-methylcyclohexyloxycarbonyl. Processes for the synthesis of amino acids containing these protecting groups and the use of these novel amino acid compounds in the preparation of peptides are also disclosed.