Synthesis, modelling, and mu-opioid receptor affinity of N-3(9)-arylpropenyl-N-9(3)-propionyl-3,9-diazabicyclo[3.3.1]nonanes

A series of N-3-arylpropenyl-N-9-propionyl-3,9-diazabicyclo[3.3.1]nonanes ( 1a-g) and of reverted N-3-propionyl-N-9-arylpropenyl isomers (2a-g), as hom ologues of the previously reported analgesic 3,8-diazabicyclo[3.2.1]octanes (I-II), were synthesized and evaluated for the binding affinity towards op ioid receptor subtypes mu, delta and kappa. Compounds 1a-g and 2a-g exhibit ed a strong selective mu -affinity with K-i values in the nanomolar range, which favourably compared with those of I and II. In addition, contrary to the trend observed for DBO-I, II, the mu -affinity of series 2 is markedly higher than that of the isomeric series 1. This aspect was discussed on the basis of the conformational studies performed on DBN which allowed hypothe ses on the mode of interaction of these compounds with the mu receptor. (C) 2000 Elsevier Science S.A. All rights reserved.