Three sets of stereoisomeric bicyclic kappa agonists with defined orientation of the pharmacophoric elements pyrrolidine and dichlorophenylacetamide were stereoselectively prepared and pharmacologically evaluated. Stereoselective reduction, reductive amination, and Mitsunobu inversions were the key steps for the establishment of the desired stereochemistry. The kappa affinity decreased in the following order depending on the N-substituent: CO2CH3 > benzyl > COCH2CH3. Bicyclic derivatives with (IS,2R, 5R)-configuration showed the highest kappa receptor affinity, which led to dihedral angles of 97 degrees and 45 degrees for the N(pyrrolidine)-C-C-N(phenylacetamide) structural element. The most potent K agonist of this series was (+)-methyl (1S,2R,5R)-8-[2-(3,4-dichlorophenyl)acetyl]-2-(pyrrolidin-1-yl)-6,8-diazabicyclo[3.2.2]nonane-6-carboxylate (ent-23, WMS-0121) with an kappa(i) value of 1.0 nM. ent-23 revealed high selectivity against the other classical opioid receptors and related receptor systems. In the [S-35]GTP gamma-S-binding assay at human kappa-opioid receptors, ent-23 was proved to be a full agonist with the same EC50 value (87 nM) as the prototypical full agonist U-69,593 (EC50 = 80 nM).
Synthesis of Bicyclic σ Receptor Ligands with Cytotoxic Activity
Enantiomeric alcohols 15 (1S,2S,5R) and ent-15 (1R,2R,5S) as well as diastereomeric methyl ethers ent-17 (1R,2R,5S) and ent-22 (1R,2S,5S) display high sigma1 receptor affinity. Cell growth inhibition of the stereoisomeric alcohols and methyl ethers against five human tumor cell lines is investigated. In particular, at a concentration of 20 muM the four methyl ethers stop completely the cell growth of