Alkylation of 3-methoxybenzenethiol (I) with 4'-methoxyphenacyl bromide (II) afforded sulfide (III). Cyclization of (III) with concomitant rearrangement in the presence of polyphosphoric acid produced a mixture of regioisomers (IV) and (V) that were separated by their different solubility in acetone. Then, Friedel-Crafts acylation of the desired insoluble isomer (IV) with 3,4,5-trimethoxybenzoyl chloride (VI) in the presence of AlCl3 provided the title ketone, which was separated from some demethylated byproduct by means of silica gel chromatography.