Azapeptide derivative

An azapeptide compound represented by the formula (1):

• ##STR3## wherein R.sup.1 represents a hydrogen atom or a protective group for a terminal amino group;
• R.sup.2 represents a phenyl group or a phenyl group substituted by one or two substituents selected from the group consisting of a lower alkyl group, halogen atom, hydroxyl group which may be protected, nitro group, amino group which may be protected and perhalo lower alkyl group;
• and R.sup.3 represents a hydroxyl group or a protective group for a terminal carboxyl group,
• wherein A is a non-natural .alpha.-amino acid selected from the group consisting of norleucine, norvaline, alloisoleucine, homoarginine, thiaproline, methionine sulfoxide, methionine sulfone, dehydroproline, homoserine, cyclohexylglycine, .alpha.-amino-n-butyric acid, cyclohexylalanine, aminophenylbutyric acid, phenylalanines in which a phenyl portion of phenylalanine is substituted by 1 or 2 of a lower alkyl, a lower alkoxy, a halogen or a nitro group, or substituted by a methlenedioxy group, .beta.-(2- or 3-thienyl)alanine, .beta.-(2- or 3-furanyl)alanine, .beta.-(2-, 3- or 4-pyridyl)alanine, .beta.-(benzothiophen-2- or 3-yl)alanine and .beta.-(1- or 2-naphthyl)-alanine;
• or a salt thereof.