An efficient synthesis of the benzhydrylpiperazine delta opioid agonist (+)-BW373U86

A diastereoselective version of Katritzkyʹs method for tertiary amine formation provides an efficient route to the highly selective, non-peptidal, delta opioid agonist (+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-hydroxybenzyl]-N,N-diethylbenzamide [(+)-BW373U86], 1.