Synthesis of Polysantol® and related sandalwood-type odorants using magnesium α-bromoketone enolates

The syntheses of the commercial sandalwood-type odorant Polysantol® and several structurally related compounds are described. The methodology followed is based on a selective and efficient magnesium-mediated aldol reaction of the starting material, α-campholenic aldehyde and different α-bromoketones. Dehydration of the resulting secondary alcohol and reduction of the carbonyl group allowed the completion of the syntheses of the target molecules in 30–56% overall yields.