Selective transformations of friedelanes isolated from cork smoker wash solids

Friedelin (1) and 3-acetoxyfriedel-3-en-2-one (4), commonly known as friedelane triterpenoids, have been isolated from cork smoker wash solids (also known as black wax) on a multi-gram scale. These compounds are valuable starting materials for the synthesis of new friedelane derivatives. Stereoselective reduction of friedelin by treatment with LiAlH₄, sodium, or catalytic hydrogenation results in the formation of both isomers of friedelinol (5 and 7) in excellent yields. Similarly, the reduction of 3-acetoxyfriedel-3-en-2-one gave epi-cerin (14) and a series of isomeric 2,3-diols or α-hydroxyketones. These transformations provide the most straightforward and convenient methods for the synthesis of A-ring functionalised friedelane derivatives using easily accessible starting materials.