Thiazolo[3,4-b]isoquinolines

An isoquinoline derivative of the formula:

• ##STR9## wherein the symbol A.sub.1 represents an isoquinol-8-yl, 3-methylisoquinol-8-yl, 3-hydroxymethylisoquinol-5-yl, 3-carboxymethylisoquinol-5-yl, quinol-5-yl, thienopyrid-3-yl, benzimidazol-5(or -6)-yl, thien-2-yl or thiazol-2-yl radical, a 4-(or 5-) carboxyalkylthiazol-2-yl radical in which the alkyl moiety is linear or branched and contains 1 to 4 carbon atoms, or a 1,3,4-thiadiazol-2-yl, pyrazol-3-yl, imidazolyl, pyrimidin-2-yl, pyridazin-3-yl or pyrazin-2-yl radical, it being understood that a monocyclic heterocyclic ring within the definition of A.sub.1 may be substituted by a linear or branched alkyl radical containing 1 to 4 carbon atoms, in the (S) or (R,S) form or a mixture thereof, or when A.sub.1 is other than thien-2-yl, a non-toxic pharmaceutically acceptable acid addition salt thereof, or, when A.sub.1 represents a 3-carboxymethylisoquinol-5-yl or 4-(or 5-)-carboxyalkylthiazol-2-yl radical, optionally substituted by an alkyl radical as hereinbefore defined, a non-toxic pharmaceutically acceptable metal salt thereof or a non-toxic pharmaceutically acceptable addition salt thereof with a nitrogen-containing base.