Abstract: New octapeptides having the formula Prot Grp-R-Trp-Ser-Tyr-R.sub.2 -Leu-Arg-Pro-R.sub.3 ; salts thereof; wherein R is Gln, Gln (bzl), His (bzl), Ser (bzl), Pro, Leu, Tyr (bzl), Ile, Cys (bzl) or Phe, R.sub.2 is D-Phe, D-Ala, D-Leu, D-Trp, D-Tyr, D-Tyr (Me), D-Ser, D-Met, D-Arg, D-Val, D-His, D-Gln, D-Phs, D-Thr, D-Pro, D-Me.sub.5 Phe or D-Asn and R.sub.3 is NH.sub.2, NH(lower alkyl), N-(lower alkyl).sub.2, NH-benzyl, NHCH.sub.2 CH.sub.2 N-(lower alkyl).sub.2 or NH-CH.sub.2 CH.sub.2 SO.sub.2 NH-benzyl; methods for their production; certain peptide intermediates and their salts used in the production thereof; and the use of said octapeptides as luteinizing hormone releasing factor antagonists.

Abstract: New hexapeptides having the formula X-Ser(benzyl)-Tyr(benzyl)-Ala-Leu-Arg-Pro-Y wherein X is t-butoxycarbonyl or benzyloxycarbonyl and Y is lower alkoxy, amino, lower alkylamino or di(lower alkyl)amino.

Abstract: New nonapeptides having the formula Prot Grp-R-Trp-Ser-Tyr-R.sub.2 -Leu-Arg-Pro-Gly-R.sub.3 ; salts thereof; wherein R is Gln, Gln (bzl), His (bzl), Ser (bzl), Pro, Leu, Tyr (bzl), Ile, Cys (bzl) or Phe, R.sub.2 is D-Phe, D-Ala, D-Leu, D-Trp, D-Tyr, D-Tyr (Me), D-Ser, D-Met, D-Arg, D-Val, D-His, D-Gln, D-Phs, D-Thr, D-Pro or D-Asn and R.sub.3 is NH.sub.2, NH(lower alkyl) or N-(lower alkyl).sub.2, methods for their production; certain peptide intermediates and their salts used in the production thereof; and the use of said nonapeptides as luteinizing hormone releasing factor antagonists.

Abstract: New pentapeptides having the formula X-R-Ser-(benzyl)-Tyr(benzyl)-R.sup.1 -Y wherein X is t-butoxycarbonyl or benzyloxycarbonyl, R is a single amino acid fragment or a dipeptide fragment utilizing amino acids selected from the group consisting of Aze, His(benzyl) and Trp; R.sup.1 is a single amino acid fragment or a dipeptide fragment utilizing amino acids selected from the group consisting of Ala, Leu and Pro and Y is lower alkoxy, hydrazino, amino, lower alkylamino or di(lower alkyl)amino with the priviso that the total number of amino acid units when R and R.sup.1 are combined is three.

Abstract: New tetrapeptides having the formula A-Ser(benzyl)-Try(benzyl)-D-Ala-Leu-R.sub.1 wherein A is t-butoxycarbonyl, cyclohexylcarbonyl, benzyloxycarbonyl and p-nitrobenzyloxycarbonyl; Ser(benzyl) is D-Ser(benzyl) or L-Ser(benzyl); Tyr(benzyl) is D-Tyr(benzyl) or L-Tyr(benzyl); Leu is D-Leu or L-Leu, and R.sub.1 is lower alkoxy, hydrazino, amino, lower alkylamino or di(lower alkyl)amino.