NEW MATERIAL: A geminally substituted thiaheterocyclic carboxylic acid of formula I (A is an aryl which is, if required, substituted with at least one of a halogen, a lower alkoxy, a carboalkoxy, a lower alkyl, an alkylamino or a phenyl; X1 is CH2, NH; R1 is COOH, a COO-alkali metal, a COO-lower alkyl, CONHSO2R2 or a 5-tetrazolyl; R2 is a lower alkyl or an aryl; m is 0, 1 or 2; p is 2-5), a salt or a stereoisomer thereof.

EXAMPLE: 4-[3-(tetrahydro-3-phenyl-3-thienyl)propyl]benzene-acetic acid.S,S- dioxide.

USE: Useful as a thromboxane receptor antagonist useful for treating thrombosis. Also effective for diabetic retinopathy.

PREPARATION: A bromophenylalkanoic acid is subjected to reduction reaction with a borane in tetrahydrofuran and by several subsequent steps a compound of formula I is obtained.