The present invention is concerned with compounds of formula ##STR00001##
the N-oxides, the pharmaceutically acceptable addition salts and the
stereochemically isomeric forms thereof, wherein X represents O, S or
NR.sup.3; R.sup.1 represents hydrogen, hydroxy, C.sub.1-6alkyl or aryl;
R.sup.2 represents hydrogen; optionally substituted C.sub.1-12alkyl;
C.sub.3-7cycloalkyl; C.sub.2-8alkenyl; aryl; Het.sup.1; or R.sup.1 and
R.sup.2 taken together may form a bivalent radical of formula
--(CH.sub.2).sub.n-- wherein n is 2, 3, 4, 5 or 6; R.sup.3 represents
hydrogen, optionally substituted C.sub.1-6alkyl, aryl, Het.sup.1; R.sup.4
represents hydrogen; hydroxy; mercapto; C.sub.1-6alkyloxy;
C.sub.1-6alkylthio; aryloxy; arylthio; Het.sup.1-oxy; Het.sup.1-thio;
optionally substituted C.sub.1-12alkyl; optionally substituted
C.sub.2-8alkenyl; optionally substituted C.sub.2-8alkynyl; optionally
substituted C.sub.3-7cycloalkyl; optionally substituted
C.sub.5-7cycloalkenyl; aryl; Het.sup.1; or -Alk-NR.sup.3R.sup.5 (i) or
--NR.sup.3R.sup.5 (ii) wherein Alk represents C.sub.1-6alkanediyl; and
R.sup.5 represents hydrogen, C.sub.1-6alkyl, aryl, Het.sup.1, (aryl or
Het.sup.1)C.sub.1-6alkyl, (aryl or Het.sup.1)carbonyl or (aryl or
Het.sup.1)C.sub.1-6alkyloxycarbonyl; aryl represents optionally
substituted indanyl, indenyl, naphtyl, 5,6,7,8-tetrahydro-2-naphtalenyl
or phenyl; Het represents an optionally substituted unsaturated
heterocycle; and Het.sup.1 represents an optionally substituted
monocyclic or bicyclic heterocycle; having retinoic mimetic activity;
their preparation, compositions containing them and their use as a
medicine.