Amino acid derivatives and antihypertensive drugs containing them

An antihypertensive composition which comprises

• 0.2-2,000 mg of at least one of the amino acid derivatives represented by the formula:
• ##STR9## wherein:
• R.sub.1 and R.sub.2 are the same or different from each other, and each individually represents hydroxyl, alkyloxy, aryloxy, aralkyloxy, alkyl, aryl, or aralkyl;
• R.sub.3, R.sub.5, R.sub.8, and R.sub.11, at least two of which are the same, or all of which are different from one another, and each individually represents hydrogen atom or lower alkyl;
• R.sub.4, R.sub.7, and R.sub.10, at least two of which are the same, or all of which are different from one another, and each individually represents a hydrogen atom, or lower alkyl, lower aryl or benzyl, which may be further substituted by OH, COOH, amino, carbamoyl, guanidino, imidazolyl, indolyl, mercapto, or alkylthio;
• R.sub.6 and R.sub.9 are the same or different from each other, and each individually represents a hydrogen atom, lower alkyl, lower aryl or benzyl;
• R.sub.12 represents hydroxyl, alkyloxy, aryloxy, aralkyloxy, amino, mono- or di-alkyl, aryl, or aralkylamino;
• and
• R.sub.6 and R.sub.7 combined together, and R.sub.9 and R.sub.10 combined together, may independently form an alkylene bridge having 2 to 4 carbon atoms, which may further contain a double bond;
• and
• a pharmaceutically acceptable carrier.