2-[(S)-(4-Chlorophenyl)(4-piperidinyloxy)methyl]pyridine (2R,3R)-2,3-dihydroxybutanedioate is used as a reagent to prepare optically active 4-[(4-chlorophenyl-2-pyridyl)methoxy]piperidine, a compound that is used as an intermediate in the synthesis of antihistamines and antiallergy agents. (S)-2-[(4-Chlorophenyl)(4-piperidinyloxy)methyl]pyridine is also an intermediate of Bepotastine besylate (B317000), a non-sedating H1-antagonist that has anti-inflammatory activity.