Anti-hypertensive agents

A new compound having the formula:

• ##STR5## wherein R is hydrogen, formyl, acetyl, propanoyl, butanoyl, phenylacetyl, phenylpropanoyl, benzoyl, cyclopentanecarbonyl, tert-butyloxycarbonyl, cyclopentanecarbonyl-L-lysyl, pyro-L-glutamyl-L-lysyl, L-lysyl, L-arginyl or pyro-L-glutamyl;
• A is D-phenylalanyl, D,L-alanyl, D-alanyl, D,L-tryptophyl, D-tryptophyl, D,L-tyrosyl, D-tyrosyl, D,L-isoleucyl, D-isoleucyl, D,L-leucyl, D-leucyl, D,L-histidyl, D-histidyl, D,L-valyl, or D-valyl, the .alpha.-amino group thereof being in amide linkage with R unless R is hydrogen;
• when R is not hydrogen, it being understood that when R is benzoyl and R.sub.2 is a residue of L-proline or a dehydroproline, A may also be L-phenylalanyl
• R.sub.1 is hydrogen or methyl;
• R.sub.2 is a residue of L-proline, L-3,4-dehydroproline, D,L-3,4dehydroproline, L-3-hydroxyproline, L-4-hydroxyproline, L -thiazolidine-4-carboxylic acid, or L-5-oxo-proline, the imino group thereof being in imide linkage with the adjacent ##STR6## and, n is 0 or 1, such that when n is 0, R.sub.1 is methyl.