[CH3:1][C:2]([CH3:15])([CH2:12][CH:13]=C)[C:3](=[O:11])[CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1.O=[O+][O-].O=O.CSC.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.C1CCN2C(=NCCC2)CC1>CO.C(Cl)Cl.CC(O)=O>[CH3:15][C:2]1([CH3:1])[C:3](=[O:11])[C:4]([C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][CH:10]=2)=[CH:13][CH2:12]1A solution of the product of Step 2 (15 g) in 70 mL of MeOH and 50 mL of CH2Cl2 was treated with a stream of ozone/oxygen until the solution turned light blue. Dimethylsulfide (20 mL) was added and the reaction mixture was stirred for 2 h at room temperature and then treated with 5 g of triphenylphosphine for an additional 0.5 h. DBU (1 mL) was then added to the reaction mixture. After stirring for 1 h at room temperature, 1 mL of AcOH was added and the reaction mixture was concentrated. The residue was dissolved in 100 mL of 20:1 hexanes/EtOAc and the solution was filtered through a pad of silica gel. The filtrate was concentrated to give 11 g of the tite compound as a yellow oil.
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