Heptapeptide oxytocin analogues

A method for preparing a heptapeptide analogue, or a pharmaceutically acceptable salt thereof, having oxytocin antagonist activity and consisting of a hexapeptide moiety S and a C-terminal .beta.-aminoalcohol residue Z bound to the moiety S by an amide bond, wherein the .beta.-aminoalcohol Z is:

• wherein Q is (CH.sub.2).sub.n --NH--A, n is 1-6 and A is H or --C(.dbd.NH)NH.sub.2 and wherein R is CH.sub.3 or C.sub.2 H.sub.5 ;
• and the moiety S is:
• ##STR22## wherein Mpa, Ile, Asn and Abu have the following meaning
• ______________________________________ Mpa 3-mercaptopropionic acid residue Ile isoleucine residue Asn asparagine residue Abu .alpha.-aminobutyric acid residue;
• ______________________________________
• and wherein X is a D-aromatic .alpha.-amino acid;
• and Y is an aliphatic .alpha.-amino acid,
• by reducing a corresponding compound wherein Z is Y:
• ##STR23## wherein M is (CH.sub.2).sub.n --N(Pht) or --(CH.sub.2).sub.n --N(P)--C(.dbd.NP)NP.sub.2 wherein one or two of the groups P are nitrogen protecting groups and the rest are hydrogen, n is 1-6, and R.sup.1 is CH.sub.3 or C.sub.2 H.sub.5,
• using a borohydride salt or a substituted borohydride or borane.