[Li+].[CH2:2]1[C:5](=[O:6])[N:4]2[C@@H:7]([C:13]([O-:15])=[O:14])/[C:8](/[O:12][C@H:3]12)=[CH:9]/[CH2:10][OH:11].P([O-])([O-])([O-])=O.[K+:21].[K+].[K+].C(O)C.P([O-])([O-])([O-])=O.[Li+].[Li+].[Li+]>O.CC(C)=O>[CH2:2]1[C:5](=[O:6])[N:4]2[C@@H:7]([C:13]([O-:15])=[O:14])/[C:8](/[O:12][C@H:3]12)=[CH:9]/[CH2:10][OH:11].[K+:21]Lithium clavulanate (5.15 g, estimated purity 95% pfa; 0.025 moles) was dissolved in water (45 mls) and cooled in an ice bath. Tripotassium orthophosphate (10.1 mls of 1 M solution; 1.2 equivalents) was added in one lot. Ethanol (32 mls) was added slowly over 1/2 hour by which time lithium phosphate had precipitated out and the pH had fallen from 8.3 to 7.3. The mixture was then made up to 800 mls with acetone over 3/4 hr. Celite (2 gm) was added and then the mixture was filtered to give a clear, colourless filtrate. This was added with rapid stirring to acetone (1750 mls) over 1 hr and the white solid was filtered off, washed with acetone (3×50 mls) and dried on a fluid bed dryer to yield potassium clavulanate (4.8 g, 82.9 pfa, 81% recovery).
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