C([O:5][C:6](=[O:25])[CH2:7][N:8]([C:14](=[S:24])[C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][C:16]=1[C:21](=[O:23])[CH3:22])[CH:9]1[CH2:13][CH2:12][CH2:11][CH2:10]1)(C)(C)C.[I-].[Na+].Cl[Si](C)(C)C>C(#N)C>[C:21]([C:16]1[CH:17]=[CH:18][CH:19]=[CH:20][C:15]=1[C:14]([N:8]([CH:9]1[CH2:10][CH2:11][CH2:12][CH2:13]1)[CH2:7][C:6]([OH:25])=[O:5])=[S:24])(=[O:23])[CH3:22]The crude ester (28.2 g) was combined with sodium iodide (16.5 g, 0.11 m) in acetonitrile (100 ml) and the mixture brought to 45° C. Chlorotrimethylsilane (11.9 g, 0.11 m) was introduced and heating was continued at 45°-52° for 26 min. The mixture was cooled, quenched with water (60 ml) and diluted with methylene chloride. The organic layer was removed, washed with water, sodium thiosulfate solution and brine, and concentrated in vacuo. Treatment of the residue with saturated sodium bicarbonate solution was followed by filtration of insoluble matter. The filtrate was washed with ethyl acetate, acidified (concentrated hydrochloric acid) and extracted (ethyl acetate). Drying and concentration of the extracts gave a residue which was purified by column chromatography or HPLC. The product was isolated as an amorphous solid.
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