[O:1]=[C:2]1[C:8]2[CH:9]=[CH:10][C:11]([C:13]([O:15][CH3:16])=[O:14])=[CH:12][C:7]=2[S:6][C:5]2[CH:17]=[CH:18][CH:19]=[CH:20][C:4]=2[NH:3]1.[OH-:21].[Ca+2].[OH-:23]>ClC1C=CC=C(C(OO)=O)C=1.C(Cl)(Cl)Cl>[O:1]=[C:2]1[C:8]2[CH:9]=[CH:10][C:11]([C:13]([O:15][CH3:16])=[O:14])=[CH:12][C:7]=2[S:6](=[O:23])(=[O:21])[C:5]2[CH:17]=[CH:18][CH:19]=[CH:20][C:4]=2[NH:3]1Dissolve 570 mg (2 mmoles) of the ester of Example 2 in a mixture of 2.3 gm of m-chloroperbenzoic acid and 75 cc of chloroform and stir for 12 hours at room temperature. Basify with calcium hydroxide. Filter and evaporate to dryness. Chromatograph the residue over silica gel eluding with 30% ethyl acetate in benzene. Collect the sulfone fractions and evaporate to dryness. Stir the residue in ether for 30 minutes, filter and dry to obtain the title product (m.p. 300°-302° C.), sintered around 295° C.).
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