synthesized a novel 7-membered ring ether derivative, which had an inserted OCH2 group between the 4- and 6-positions of the morphinan skeleton. The derivative with a 7-membered ring ether, 4,6′-epoxymorphinan, has a more fixed chair form than the 4,5-epoxymorphinan. In addition, we found a new cleavage reaction of the 4,5-epoxy ring in naltrexone, and also obtained a highly strained novelconjugated ketone
A modi. cation of the message site in the skeleton of naltrexone was carried out to improve the potency and selectivity of the compound for an opioid receptor subtype. In the course of conversion, we synthesized 7-membered ring ether derivatives, which had an inserted OCH2 group between 4- and 6-positions of morphinan skeleton. One of the 7-membered ring ether derivatives possessed more potent antagonistic activity than naltrexone for the l opioid receptor. Another compound possessing 17-methyl group derived from noroxycodone may be a l opioid receptor partial agonist and showed analgesic activity. We are currently examining the subtype selectivity of these compounds. (C) 2008 Elsevier Ltd. All rights reserved.