Novel ligand antagonists of the RAR receptors have the following
structural formula (I): ##STR00001## in which A is a CH.sub.2, CHOH,
C.dbd.O or C.dbd.N--OH radical or a sulfur or selenium atom; B is a
radical selected from among those of formulae (a) to (f): ##STR00002##
and Ar is a radical selected from among those of formulae (g) to (i):
##STR00003##