The hydroboration-oxidation of abietic acid

Abstract

Monohydroboration-oxidation of abietic acid and methyl abietate with both diborane and t-2,3-dimethylbutylborane leads to preferential attack on the 7,8-double bond to give 7-hydroxy-8(14)-enes, e.g., (IIIa). Dihydroboration-oxidation with these reagents yields mainly the 7β,14β-dihydroxy derivatives, e.g., (XIXa), with smaller amounts of the 7α, 14α-dihydroxy-compounds and a third 7,14-diol of unknown stereochemistry. The dihydroboration reactions are of interest, since it is shown that at least one of the products is derived by migration of the 13,14-double bond of abietic acid to the 8,14-position during hydroboration. Some reactions of the hydroxyabietic acid derivatives are described.