Organic compounds

A compound of formula I, ##STR53## wherein R.sub.1 is (i) H,

• (ii) NH.sub.2,
• (iii) H--Ala--NH--;
• H--Tyr--NH--;
• H--Cys--NH--;
• H--Val--NH--;
• H--Lys--NH--;
• H--(.alpha.-amino-isobutyryl)--NH--;
• H--Phe--NH
• (iv) NH.sub.2 --NH--CO--NH--;
• (v) C.sub.6 H.sub.5.NH--CO--Gly--NH--;
• H--Ala--Gly--NH--;
• H--Val--Gly--NH--;
• H--.alpha.--phenyl--Gly--NH--,
• (vi) R.sub.2 --A--CO--NH--,
• wherein
• R.sub.2 is lower alkyl, phenyl, or phenyl substituted by halogen, hydroxy, amino lower alkyl or lower alkoxy,
• A is a direct bond, alkylene containing up to 6 carbon atoms or --NH--,
• (vii) R.sub.2 --Ala--NH--;
• R.sub.2 --Ala--Gly--NH--;
• wherein R.sub.2 is as defined above,
• (viii) C.sub.6 H.sub.5.A.sup.I.CO--M--NH--,
• wherein
• A.sup.I is an alkylene chain of up to 6 carbon atoms, and
• --M-- is --(mono- or di-Hal)--Phe, --Gly-- or --Ala--,
• (ix) T--(mono- or di-Hal)--Phe--NH, wherein T-- is H--, H--Val-- or benzoyl--,
• (x) ##STR54## wherein A.sup.I is as defined above, and
• --L-- is --Val--(mono- or di-Hal)-- Phe--.alpha.--phenyl--Gly--, and
• n is an integer between 4 and 10,
• each B is hydrogen or the two radicals B form a direct bond,
• X is --Lys--, or --Nle--, and
• Y is --Asn--, --Gln-- or --Thr--, and
• Z signifies the radicals:
• (i) --CO--asparaginol;
• --CO--leucinol;
• --CO--iso-leucinol;
• --CO--valinol;
• --CO--norleucinol;
• --CO--glutaminol;
• --CO--threoninol;
• (ii) --CO--Leu;
• --CO--Ser;
• --CO--Iso--Leu;
• --CO--Val, and their corresponding amides, wherein the amide portion signifies the radical --CO--NR.sub.4 R.sub.5 (wherein R.sub.4 and R.sub.5 independently are hydrogen or lower alkyl) or the radical ##STR55## (wherein n is as defined above);
• (iii) --CO--ThrOR.sub.3 or --CO--SerOR.sub.3 (wherein R.sub.3 is lower alkyl);
• or
• (iv) --CO--NH--(CH.sub.2).sub.k --OH (wherein k is an integer between 2 and 6), or ##STR56## (wherein 1.sub.1 and 1.sub.2 independently signify a whole number from 1 to 6);
• wherein in formula I the unit containing radicals R.sub.1, X, Y and Z, as well as in the remaining units of the peptide sequence, at least one unit may be present in D form,
• with the proviso that when R.sub.1 is H--Cys--NH or H--(D)--Cys--NH, B--B is other than a direct bond,
• or a pharmaceutically acceptable acid addition salt or complex thereof.