AY-31,637 may be synthesized by either of two routes: 1) Dilithiation of 2,4-thiazolidinedione (I) with two equivalents of n-butyllithium, followed by sulfonylation with 2-naphthylsulfonyl chloride (VI). 2) Coupling of 2-mercaptonaphthalene (III) and 5-bromo-2,4-thiazolidinedione (II) by the addition of two equivalents of lithium diisopropylamide gives 5-(2-naphthylthio)-2,4-thiazolidinedione (IV). Oxidation of this compound with excess hydrogen peroxide in acetic acid at 60 C gives the corresponding sulfone, AY-31,637.