Classical/nonclassical hybrid cannabinoids:: Southern aliphatic chain-functionalized C-6β methyl, ethyl, and propyl analogues

The stereoelectronic requirements for interaction of the southern aliphatic hydroxyl of cannabimimetic pharmacophores with the CB1 and CB2 receptors are explored. The stereoselective syntheses of three series of classical/nonclassical hybrid cannabinoids are described. These compounds were designed to investigate the importance of the southern aliphatic hydroxyl (SAH) pharmacophore for cannabimimetic activity. Variation in the chain length of the SAH moiety in these 6 beta-(hydroxyalkyl)dihydrobenzopyran analogues, from 6 beta-hydroxymethyl to 6 beta-(omega-hydroxyethyl) and 6 beta-(omega-hydroxypropyl), and the effects of replacing the hydroxyl functionality by hydride and iodide are reported. Our results indicate that the SAH pharmacophore has less pronounced effects than the C-3 aliphatic chain on cannabinoid activity. Furthermore, it appears that this southern molecular component is capable of interacting with two different subsites on the receptor and that the nature of this interaction is determined by the terminal substituent on the C-6 beta alkyl group. One of the subsites can accommodate the relatively polar SAH pharmacophore, while the second subsite interacts with more hydrophobic C-6 beta substituents and can accommodate large spherical pharmacophores separated by three methylene carbons from the tricyclic cannabinoid template.