Aromatic replacements for cyclohexane moiety

The analog containing benzoyl in place of cyclohexanoyl was described in one of the early PZQ patents. Interestingly the patent says this (column 2, top): "[The enantiopure compound] exhibits its althelmintic activity on [organism] in a dose which is up to five times smaller than that of the racemic [compound]. This effect could not be expected, since one would anticipate a doubling of the efficiency at most, if only one isomer were active."