Photoinduced cyclization of 3β-acetoxy-C(14a)-homo-B-norlanosta-8(14a),9(11)-diene as a route towards B(9a)-homo-C-norlanostane derivatives

The synthesis of diketones $\text{6}$, $\text{7}$ and $\text{8}$ starting from diene $\text{3}$ by photochemical cyclization followed by RuO₄ oxidation is described and stereochemistry of products is proposed.