[CH3:1][N:2]([CH3:20])[CH2:3][C:4]1([C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)[CH2:13][CH2:12][C:7]2(OCC[O:8]2)[CH2:6][CH2:5]1>OS(O)(=O)=O>[CH3:20][N:2]([CH2:3][C:4]1([C:14]2[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=2)[CH2:5][CH2:6][C:7](=[O:8])[CH2:12][CH2:13]1)[CH3:1]The title compound of step 5 (5.40 g, 19.6 mmol) was dissolved in 5% H2SO4 (300 mL) and stirred for 1 d at RT. The solution was then washed with ether three times and the ether phase discarded. The aqueous phase was made alkaline with 5N NaOH with ice cooling and extracted with dichloromethane three times. The organic phase was washed with a little water, dried over Na2SO4 and concentrated to low volume in a vacuum.
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