[C:1]([O:5][C:6]([N:8]1[CH2:14][CH:13]([OH:15])[CH2:12][S:11](=[O:17])(=[O:16])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].CC(C)=O.OS(O)(=O)=O.O=[Cr](=O)=O.CO>CC(C)=O>[C:1]([O:5][C:6]([N:8]1[CH2:14][C:13](=[O:15])[CH2:12][S:11](=[O:16])(=[O:17])[CH2:10][CH2:9]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]4-N-(t-Butyloxycarbonyl)-1,1-dioxo-6-hydroxy -2,3,4,5,6,7-hexahydro-1,4-thiazepine (10.0 g, 37.7 mmole) from Example 5, was dissolved in 110 mL of acetone, cooled to 0° C. and treated with 18.8 mL of freshly prepared Jones reagent. The reaction was stirred at ambient temperature for three hours and then treated with 5 mL of methanol. After 15 minutes, the reaction was filtered through magnesium sulfate and the filtrate immediately concentrated. The residue was filtered through a pad of silica gel using 3:1 chloroform-ethyl acetate to obtain the produce (9.67 g, 87%) D.C.I.M.S. 264(M+H) M.P. 172°-173° C.
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