Compounds according to formula (I) wherein the radicals R1, R2 and R3 are as herein defined, and wherein Ar represents an aryl group or heteroaryl group, preferably phenyl, n is 1 or 2, and the radical X represents a group selected from &mdash；C(Ra)(Rb)&mdash；, &mdash；C(Ra)(Rb)&mdash；C(Ra)(Rb)&mdash；, &mdash；C(Ra)&boxH；C(Ra)&mdash；, OC(Ra)(Rb)&mdash； or SC(Ra)(Rb)&mdash；. These compounds and their pharmaceutical acceptable salts are used in pharmaceutical compositions as prostaglandine D2 receptor antagonists useful in the treatment of CRTH2-mediated diseases such as respiratory, inflammatory or allergic conditions among others.
