[CH3:1][C:2]([CH3:21])=[CH:3][C:4]1[CH:5]=[C:6]([CH:11]=[CH:12][C:13]=1[O:14]C1CCCCO1)[C:7]([O:9][CH3:10])=[O:8].CC1C=CC(S([O-])(=O)=O)=CC=1.C1C=C[NH+]=CC=1>CO>[OH:14][C:13]1[CH:12]=[CH:11][C:6]([C:7]([O:9][CH3:10])=[O:8])=[CH:5][C:4]=1[CH:3]=[C:2]([CH3:21])[CH3:1]To a stirred mixture of 66.20A (0.460 g, 2 mmol) in MeOH (8 mL) was added PPTS (0.04 g, 0.2 mmol). The reaction mixture was then stirred for 24 hours and then concentrated in vacuo. The residue was purified on silica gel (0-20% EtOAc in hexanes) to yield 66.20B as a colorless oil (0.320 g, 98% yield).
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