Functionalization of the 6,14-bridge of the orvinols. 2. Preparation of 18- and 19-hydroxyl-substituted thevinols and their treatment with benzyl bromide

The etheno bridge of a thevinone was treated with BH3 and H2O2 to give both the 18- and 19-hydroxyl- substituted thevinols. Selective benzylation of the primary 20-hydroxyl over the 19-hydroxyl was successful; however, benzylation of the 18-hydroxylated product led to a reaction at the more hindered alcohol. Thus, the 6,14-bridge of the Diels-Alder products of thebaine can be hydroxylated, which opens up these positions for further chemical manipulation.