FC(F)(F)S(O[C:7]1[N:8]=[C:9]2[C:14](=[C:15]3[C:20]=1[C@@H:19]([CH3:21])[CH2:18][C:17]([O:24][CH3:25])([O:22][CH3:23])[C@@H:16]3[OH:26])[CH:13]=[C:12]([O:27][CH3:28])[CH:11]=[CH:10]2)(=O)=O.C(N(CC)CC)C.C(O)=O>O1CCOCC1>[CH3:28][O:27][C:12]1[CH:11]=[CH:10][C:9]2[C:14](=[C:15]3[C:20](=[CH:7][N:8]=2)[C@@H:19]([CH3:21])[CH2:18][C:17]([O:22][CH3:23])([O:24][CH3:25])[C@@H:16]3[OH:26])[CH:13]=1Tetrakistriphenylphosphine palladium (778 mg, 673 mmol, 0.04 equiv) was added to a deoxygenated solution of (7S, 10R)-7,8,9,10-tetrahydro-2,9,9-trimethoxy-7-methyl-6,10-phenanthridinediol 6-(trifluoromethanesulfonate) (13, 7.60 g, 16.8 mmol, 1 equiv) and triethylamine (9.40 mL, 67.3 mmol, 4.00 equiv) in dioxane (300 mL) at 23° C. The resulting solution was deoxygenated by alternately evacuating the reaction vessel and flushing with argon (5×). Formic acid (1.70 mL, 43.8 mmol, 2.63 equiv) was added slowly over 5 min via syringe and the resulting solution was heated at reflux for 20 min, then was allowed to cool to 23° C. The reaction mixture was partitioned between saturated aqueous sodium chloride solution (300 mL) and ethyl acetate (300 mL). The aqueous layer was separated and further extracted with ethyl acetate (2×300 mL). The combined organic layers were dried over sodium sulfate and were concentrated in vacuo. The residue was purified by flash column chromatography (ether initially, grading to 20% ethyl acetate-ether) to provide (7S, 10R)-7,8,9,10-tetrahydro-2,9,9-trimethoxy-7-methyl-10-phenanthridinol (15) as a white foam (mp 135°-136° C., 4.94 g, 97%).
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