DOUBLE DIASTEREOSELECTION IN INTRAMOLECULAR PHOTOCYCLOADDITIONS - A RADICAL REARRANGEMENT APPROACH TO THE TOTAL SYNTHESIS OF THE SPIROVETIVANE PHYTOALEXIN (+ -)-LUBIMINOL/

The highly stereoselective total synthesis of the phytoalexin (+/-)-lu biminol (1) has been accomplished. The synthesis relies on three pivot al transformations: (1) a conjugate addition-cyclization reaction to p repare a highly functionalized 2-carbomethoxycyclopentenone as a photo cycloaddition substrate, (2) a double diastereoselective intramolecula r photocycloaddition for a stereoselective intramolecular photoadditio n reaction which establishes the central quaternary spirocenter, and ( 3) the transformation of the photoadduct into the required spiro[5.4]d ecane through a radical fragmentation-rearrangement reaction.