Two 1-(Arylacetyl)-2-(aminomethyl)piperidine Derivatives, a Novel Class of Highly Selective κ-Opioid Analgesics

The single-crystal X-ray structures of (+)-1-{(2R)-1-[(3,4-dichlorophenyl)acetyl]piperidin-2-ylmethyl}pyrrolidinium chloride monohydrate (C₁₈H₂₅Cl₂N₂O⁺.Cl⁻.H₂O; BRL-52536A) and (−)-1-{(2S)-1-[(3,4-dichlorophenyl)acetyl]piperidin-2-ylmethyl}piperidinium chloride (C₁₉H₂₇Cl₂N₂O⁺.Cl⁻; BRL-52781A) have been determined. BRL-52536A is the inactive stereoisomer of BRL-52537A, the highly selective and potent lead compound of the series. The pharmacophore N—C—C—N(_sp²) torsion angle is (+)-synclinal in the 2S configuration.

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