Substituted phenoxyisobutyric acids and esters

A substituted phenoxyisobutyric acid or ester selected from those of formula I:

• ##STR42## wherein:
• X represents oxygen;
• A represents a single bond or an alkylene radical having 1 to 9 carbon atoms inclusive in a straight or branched chain optionally including a double bond, a cyclopropyl radical, an oxygen atom or a carbonyl radical, or optionally substituted by halogen or hydroxy;
• R represents hydrogen or alkyl having 1 to 6 carbon atoms inclusive in a straight or branched chain and optionally substituted by one or two hydroxy;
• R.sub.1 and R.sub.3 ;
• together form a (CH.sub.2).sub.n bridge wherein n is 1 or 2;
• each of R.sub.2 and R.sub.6, which may be identical or different, represents hydrogen or methyl;
• each of R.sub.4 and R.sub.5, which may be identical or different, represents alkyl having 1 to 6 carbon atoms inclusive in a straight or branched chain;
• R.sub.7 represents hydrogen or CH.sub.3 CO--, C.sub.2 H.sub.5 O--CH.sub.2 --, or benzyl;
• and
• Z represents hydrogen, halogen, alkyl or alkoxy, each containing 1 to 5 carbon atoms inclusive in a straight branched chain;
• and, when they exist, its corresponding enantiomers and diastereoisomers,
• and also its physiologically-tolerable salts with suitable bases.