Synthesis and opioid binding properties of 2-chloroacrylamido derivatives of 7,8-dihydromorphinans

14β-2-chloroacrylamido-7,8-dihydromorphinones 7 and 8 and the corresponding 6β-7,8-dihydromorphinans 19 and 20 were prepared and the binding affinities to μ, δ and κ receptors in bovine striatal membranes were determined. Only 20 produced wash-resistant inhibition of m binding despite the fact that it formed adducts with N-acetylcysteine at pH 10 and not at pH 8.