The Vilsmeier-type reaction of 1-methylindole (I) with 5-(1-pyrrolidinocarbonyl)-4,5,6,7-1H-tetrahydrobenzimidazole hydrochloride (II) and phosphorous oxychloride in 1,2-dichloroethane gives (?-5-[(1-methyl-3-indolyl)carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazol e (III). Optical resolution of (III) with (+)-dibenzoyltartaric acid (DIBTA) in DMF-H2O, followed by exchange of the salt affords YM060.