The crystal structure of the dihydrobromide heptahydrate of nor-binaltorphimine (17, 17′-bis(cyclopropylmethyl)-6,6′,7,7′-tetrahydro-4,5α: 4′,5′α-diepoxy-6,6′-imino[7,7′ bimorphinan]-3,3′,14,14′-tetraol)is presented. This structure is the first reported structure of a rigid bivalent opioid ligand. Two morphinan pharmacophores are connected by a rigid spacer, the pyrrole ring. The nor-binaltorphimine structure itself shows unique, high selectivity as a kappa opioid receptor antagonist. Crystal data: P32, Z = 3, a = b = 20.223 (4), c = 9.541(7) Å, α = β = 90°, γ = 120°; R = 0.079 (1765 reflections, Fobs > 1σ(F)).
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This research was partially supported by the National Institute on Drug Abuse (DA 02659) to PSP. Helpful discussionsw ith Professor Doyle Britton, University of Minnesota, about crystallographic aspects of this work are greatly appreciated.