A compound is of formula (I), in which: A1 to A4, E1
and E2 each independently represent hydrogen or an optionally-substituted
hydrocarbon group; B1 and B2 each independently represent
a single bond, an oxygen atom or an optionally-substituted hydrocarbon group; MG1
and MG2 each independently represent an optionally-substituted
ring system; CG is a divalent or polyvalent chiral group. The optically active
compound may be used as a doping agent for liquid crystals for a wide range of
applications including solid state cholesteric filters for projection displays,
circular polarisers, optical filters, etc.
##STR1##
