P-Glu-Trp-Ser-Tyr-D-Lys-Leu-Arg-Pro-Gly-NH.sub.2 and intermediates

A compound selected from the class consisting of

• L-p-Glu-L-Trp-L-Ser-L-Tyr-D-Lys-L-Leu-L-Arg-L-Pro-Gly-NH.sub.2 (I)
• and
• R.sup.4 -L-p-Glu-L-Trp(R.sup.6)-L-Ser(R.sup.3)-L-Tyr(R.sup.2)-D-Lys(R.sup.5)-L-Leu -L-Arg(N.sup.G -R.sup.1)-Pro-Gly-X (II)
• and its non-toxic salts;
• wherein
• R.sup.1 is a protecting group for the N.sup..delta. , N.sup..omega. and N.sup..omega. .sup.' nitrogen atoms of arginine selected from the group consisting of nitro, tosyl, benzyloxycarbonyl, adamantyloxycarbonyl and tert-butyloxycarbonyl or R.sup.1 is hydrogen;
• R.sup.2 is a protecting group for the phenolic hydroxyl group of tyrosine selected from the group consisting of tert-butyl, tetrahydropyranyl, trityl, benzyl, 2,6-dichlorobenzyl, 4-bromobenzyloxycarbonyl and benzyloxycarbonyl or R.sup.2 is hydrogen;
• R.sup.3 is a protecting group for the alcoholic hydroxyl group of serine and is selected from the group consisting of acetyl, benzoyl, tetrahydropyranyl, tert-butyl, trityl, 2,6-dichlorobenzyl and benzyl or R.sup.3 is hydrogen;
• R.sup.4 is selected from the group consisting of hydrogen or an .alpha.-amino protecting group;
• R.sup.5 is a protecting group for the side chain amino substituent of lysine selected from the class consisting of 2-chlorobenzyloxycarbonyl, benzyloxycarbonyl, tosyl, t-amyloxycarbonyl, t-butyloxycarbonyl;
• or R.sup.5 is hydrogen;
• R.sup.6 is selected from the class consisting of hydrogen and formyl;
• and
• X is selected from the group consisting of NH.sub.2, O-(lower)-alkyl, O-benzyl and an anchoring bond linked to a solid polystyrene resin represented by one of the formula ##SPC3##
• wherein said polystyrene resin is cross linked through the phenyl group on each second carbon atom of the alkyl chain of said polystyrene and said symbol .phi. means phenyl, with the proviso that at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.5 and R.sup.6 is a protecting group.