Synthesis, stereochemistry, and opioid receptor binding activity of heterocyclic analogues of BW373U86

The synthesis of a series of heterocyclic analogues of (±)-4-((αR*)-α-((2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazmyl)-3-hydroxybenzyl)-N,N-diethylbenzarrude (BW373U86) for screening against opioid receptors is described. The intermediate α-heterocyclic benzyl alcohols 24 were synthesized either by low temperature reaction of lithioheterocycles with 3-((tert-butyldimethylsilyl)oxy)benzaldehyde (10) or by reaction of 3-((tert-butyldimethylsilyl)oxy)phenylmagnesium bromide (19) with heterocyclic carbaldehydes. The α-heterocyclic benzyl alcohols 24 were converted to chloromethines (25) with thionyl chloride and used to alkylate with trans-1-allyl-2,5-dimethylpiperazine (5) to give diastereomeric pairs of the target compounds. The bromoheterocycles were then derivatized to produce amides. Compounds that are potent and selective for the 5 or μ opioid receptors and some mixed δ/μ analogues are reported.