A process for preparing (-) - 5- (1H-pyrrol-1-yl) -2 - [[(4-methoxy-3-methyl-2-pyridyl) methyl] sulfinyl] -1-hydrobenzimidazole or (+) -5- (1 H -pyrrol-1-yl) -2 - [[(4-methoxy-3-methyl-2-pyridyl) methyl] sulfinyl] -1-hydro-benzimidazole of formula I ** Formula ** comprising oxidize a prochiral sulfide of formula II in chloroform in the presence of an oxidant, a base and a chiral titanium complex,Un procedimiento para preparar el (-)-5-(1H-pirrol-1-il)-2-[[(4-metoxi-3-metil-2-piridil)metil]sulfinil]-1-hidrobencimidazol o (+)-5-(1H-pirrol-1-il)-2-[[(4-metoxi-3-metil-2-piridil)metil]sulfinil]-1-hidro-bencimidazol de fórmula I **Fórmula** que comprende oxidar un sulfuro proquiral de fórmula II en cloroformo en presencia de un oxidante, una base y un complejo de titanio quiral,
