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.