Indol-3-ylcycloalkyl Ketones: Effects of N1 Substituted Indole Side Chain Variations on CB2 Cannabinoid Receptor Activity

Several 3-acylindoles with high affinity for the CB2 cannabinoid receptor and selectivity over the CB1 receptor have been prepared. A variety of 3-acyl substituents were investigated, and the tetramethylcyclopropyl group was found to lead to high affinity CB2 agonists (5, 16). Substitution at the N1-indole position was then examined. A series of aminoalkylindoles was prepared and several Substituted aminoethyl derivatives were active (23-27, 5) at the CB2 receptor. A study of N1 nonaromatic side chain variants provided potent agonists at the CB2 receptor (16, 35-41, 44-47, 49-54, and 57-58). Several polar side chains (alcohols, oxazolidinone) were well-tolerated for CB2 receptor activity (41, 50), while others (amide, acid) led to weaker or inactive compounds (55 and 56). N1 aromatic side chains also afforded several high affinity CB2 receptor agonists (61, 63, 65, and 69) but were generally less potent in all in vitro CB2 functional assay than were nonaromatic side chain analogues.