The present invention is concerned with compounds of formula the N-oxides, the pharmaceutically acceptable addition salts and the stereochemically isomeric forms thereof, wherein X represents O, S or NR3; R1 represents hydrogen, hydroxy, C1-6alkyl or aryl; R2 represents hydrogen; optionally substituted C1-12alkyl; C3-7cycloalkyl; C2-8alkenyl; aryl; Het1; or R1 and R2 taken together may form a bivalent radical of formula —(CH2)n— wherein n is 2, 3, 4, 5 or 6; R3 represents hydrogen, optionally substituted C1-6alkyl, aryl, Het1; R4 represents hydrogen; hydroxy; mercapto; C1-6alkyloxy; C1-6alkylthio; aryloxy; arylthio; Het1-oxy; Het1-thio; optionally substituted C1-12alkyl; optionally substituted C2-8alkenyl; optionally substituted C2-8alkynyl; optionally substituted C3-7cycloalkyl; optionally substituted C5-7cycloalkenyl; aryl; Het1; or -Alk-NR3R5 (i) or —NR3R5 (ii) wherein Alk represents C1-6alkanediyl; and R5 represents hydrogen, C1-6alkyl, aryl, Het1, (aryl or Het1)C1-6alkyl, (aryl or Het1)carbonyl or (aryl or Het1)C1-6alkyloxycarbonyl; aryl represents optionally substituted indanyl, indenyl, naphtyl, 5,6,7,8-tetrahydro-2-naphtalenyl or phenyl; Het represents an optionally substituted unsaturated heterocycle; and Het1 represents an optionally substituted monocyclic or bicyclic heterocycle; having retinoic mimetic activity; their preparation, compositions containing them and their use as a medicine.