C[O:2][C:3]1[CH:4]([C:15]([O:17][CH3:18])=[O:16])[C:5]2[C:10]([CH2:11][CH:12]=1)=[CH:9][CH:8]=[C:7]([O:13][CH3:14])[CH:6]=2.C(O)(=O)C(O)=O.CO>O>[OH:2][C:3]1[CH2:12][CH2:11][C:10]2[C:5](=[CH:6][C:7]([O:13][CH3:14])=[CH:8][CH:9]=2)[C:4]=1[C:15]([O:17][CH3:18])=[O:16]A mixture of II (0.124 mole), oxalic acid (0.124 mole), 400 ml. methanol and 120 ml. water was warmed until solution occurred. This solution was then stirred at 20° C. for 18 hours. The resultant mixture was warmed again to solution and then concentrated. The residue was treated with dilute potassium carbonate and extracted with methylene chloride. The extracts were dried (MgSO4), filtered and concentrated to give III (~100%). Two recrystallizations of a small sample from methanol gave an analytical sample; mp 48.0°-48.5° C.
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