The reaction of 2-hydroxy-4-(3-methyl-2-butenyloxy)acetophenone (I) with ethyl bromoacetate (II) by means of KOH in acetone gives 2-ethoxycarbonylmethoxy-4-(3-methyl-2-butenyloxy)acetophenone (III), which is then condensed with 4-(3-methyl-2-butenyloxy)benzaldehyde (IV) by means of KOH in ethanol.