A practical synthesis of thebaine and oripavine has been developed from codeine and morphine, respectively. Attempts to use a codeinone intermediate gave poor yields; however, methylation of the potassium salt of codeine to give codeine methyl ether followed by oxidation with gamma-MnO2 gave thebaine in 67% yield from codeine. Similarly, the potassium salt of the di-O-anion of morphine was selectively alkylated to give morphine 6-methyl ether (heterocodeine) in better than 90% yield. Hetercodeine was then acetylated and oxidized to oripavine 3-acetate which was hydrolyzed to give oripavine in 73% yield from morphine.