Peptide analogues

A 1,3-dithiane compound of formula I

• R.sup.1 --Z--NR.sup.2 --CHR.sup.3 --CR.sup.4 --(CH.sub.2).sub.o --CE--R.sup.6
• in which
• R.sup.1 is A--O--CO--, A--SO.sub.2 --CH.sub.2 --CH(CH.sub.2 --C.sub.6 H.sub.5)--CO--, 4--A--O--CO--NH--piperidinocarbonyl, 4-amino-piperidinocarbonyl, A--O--CO--NH--C(CH.sub.3).sub.2 --CH.sub.2 --CO--, H.sub.2 N--C(CH.sub.3).sub.2 --CH.sub.2 --CO-- or morpholinocarbonyl;
• Z is 1 or 2 amino acid residues which are linked together in the manner of a peptide and are selected from the group consisting of .beta.Ala, Cal, S-A-Cys, Gln, His, Leu, Mal, Met, Met(O).sub.2, Nle, Nva, Phe, Ser, Thr and Val, wherein one of these radicals may also be replaced by Pla;
• R.sup.2 is H;
• R.sup.3 is cyclohexylmethyl;
• R.sup.4 is (H,OH);
• o is 1, 2, 3 or 4;
• E is --S--(CH.sub.2).sub.3 -- or --SO.sub.2 --(CH.sub.2).sub.3 --SO.sub.2 --;
• R.sup.6 is H or A;
• and
• A is alkyl or 1-4 carbon atoms;
• or
• an acid addition salt thereof.