Methylation of methyl (+)-lactate (I) followed by thioacetylation and acidic hydrolysis affords (-)-thiolactic acid (IV). Reaction of 3-pyridinecarboxyaldehyde (V) with methylamine in toluene under the azeotropic condition provides the imine (VI), which when condensed with (IV) affords (+)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one (VII). Treatment of (VII) with aqueous HCl/isopropanol results in the precipitation of SM-12502.