As one of continuous synthetic studies on naturally occurring spiro compounds, we describe stereoselective total synthesis of the hydroxylated spirovetivane-type phytoalxins, lubiminol (2) and oxylubimin (4) in racemic form. 1. Total Synthesis of (±)-Lubiminol (2) The previously reported spiro-enone (8) was transformed into 14 via 13 by a several-steps sequence. The three-carbon unit introduction at C-2 in 14 was followed by catalytic hydrogenation to give 9 as a single diastereoiosmer, which was converted into (±)-lubiminol (2). 2. A New Method for α'-Hydroxylation of α,β-Unsaturated Ketones We have developed a novel method for introduction of hydroxyl group to the α'-position of α,β-unsaturated ketones by means of TPPO oxidation of their silyl enol ethers. 3. Total Synthesis of (±)-Oxylubimin (±)-Oxylubimin (4), the highest oxidized spirovetivane-type phytoalexin, was also totally synthesized with high stereoselectivity usig the above mentioned hydroxylation method as a crucial step starting the enone (8).
