[S:1]1[CH2:5][CH2:4][CH:3]([CH2:6][CH2:7][CH2:8][CH2:9][C:10]([NH:12][CH2:13][CH2:14][CH2:15][C:16]([O:18]C)=[O:17])=[O:11])[S:2]1.[OH-].[Na+]>CO>[S:1]1[CH2:5][CH2:4][CH:3]([CH2:6][CH2:7][CH2:8][CH2:9][C:10]([NH:12][CH2:13][CH2:14][CH2:15][C:16]([OH:18])=[O:17])=[O:11])[S:2]1The reaction was effected as described in Example 49, but using 0.65 g of methyl 4-[5-(1,2-dithiolan-3yl)pentanoylamino]butanoate (prepared as described in Example 73), 13 ml of methanol and a 1N aqueous solution of sodium hydroxide. The solvent was removed from the reaction mixture by distillation under reduced pressure. Water was added to the residue. After neutralisation with 2N aqeous hydrochloric acid, the resulting mixture was extracted with ethyl acetate. The extract was washed with a saturated aqueous solution of sodium chloride and then dried over anhydrous sodium sulfate. Ethyl acetate was removed from the extract by distillation under reduced pressure. The residue was recrystallized from ethyl acetate, to give 0.28 g of the title compound as yellow crystals, melting at 56 to 58° C.
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