Methylation-Ring Opening of 3,3-Disubstituted 2,3-Epoxy Alcohols. Synthesis of Chiral Quaternary Fragments for Assembly of Briaran Diterpenes.

Abstract Two chiral quaternary carbon-containing fragments suitable for elaboration to the briaran diterpenes were obtained by regioselective methylation of functionalized 3,3-disubstituted 2,3-epoxy-1-ols. The factors which favor methylation at the more hindered position of a trisubstituted 2,3-epoxy alcohol were determined.