Access to 7β-analogs of codeine with mixed μ/δ agonist activity via 6,7-α-epoxide opening

(−)-Codeine 1 was converted into previously unknown 7β-methyl-7,8-dihydrocodeine/morphine derivatives such as 13 via classical diaxial opening of α-epoxide 3. Several analogs exhibited dual μ/δ-agonist activity.