3-Methoxyphenethylamine (I) was converted into formamide (II) upon refluxing in ethyl formate. Subsequent cyclization of (II) in hot polyphosphoric acid produced the dihydroisoquinoline (III). This was subjected to a tandem Mannich-Michael condensations by refluxing in methyl vinyl ketone (IV) to yield the benzoquinolizinone system (V). The desired (S)-enantiomer (VI) was then isolated by crystallization of the diastereoisomeric salts with (-)-di-p-toluoyl-L-tartaric acid in EtOAc. Condensation of (VI) with methylamine in the presence of TiCl4, followed by reduction of the intermediate imine with NaBH4 provided amine (VII). This was finally converted to the target sulfonamide by treatment with methanesulfonyl chloride and Et3N.