[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+].CO.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 (5.6 gm, estimated purity 88.8% pfa 0.025 M) was dissolved in water (45 mls) and the resulting pale-red-brown solution was cooled in an ice bath. Tripotassium orthophosphate (10.1 mls of 1 M solution, 1.2 equivalents) was added in one lot and methanol (18 mls) added over 1/2 hr with a small quantity of lithium phosphate (ca. 1 mg) for seeding. As lithium phosphate separated out the pH dropped from 8.7 to about 7.5. Acetone was added over 3/4 hr to 800 mls. The material that separated out was quite orange-brown at this point and the supernatant a very pale yellow. Celite (2 g) filtration gave a clear solution which was added to acetone (1750 mls) with vigorous stirring over 1 hr. The white solid was filtered off leaving a very pale yellow filtrate. Washing with acetone (3×50 ml) and fluid bed drying gave potassium clavulanate (4.1 g, 84% pfa, 69% recovery).
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