Cl[C:2]([N:4]=[C:5]=[O:6])=[O:3].[OH:7][NH:8][C:9](=[O:20])[N:10]([CH:17]([CH3:19])[CH3:18])[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1.C(N(CC)CC)C.C(=O)([O-])[O-].[K+].[K+]>C1COCC1.C(Cl)Cl>[CH3:19][CH:17]([N:10]([C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1)[C:9]([N:8]1[C:5](=[O:6])[NH:4][C:2](=[O:3])[O:7]1)=[O:20])[CH3:18]A solution of chlorocarbonyl isocyanate (5.0 g, 0.047 mol) was added dropwise to a slurry of the title compound of Step A (9.2 g, 0.047 mol) and triethylamine (5.3 g, 0.052 mol) in 200 mL of THF while maintaining the reaction temperature below 30° C. using an ice bath. After 2 hours, TLC showed the presence of starting material. Another 0.5 g of chlorocarbonyl isocyanate was added, and the reaction mixture was stirred for another hour. At that point, TLC showed still the presence of starting material. The reaction mixture was filtered to, remove solids, and the filtrate was stripped to dryness and then extracted with 1N HCl and ether. Upon evaporation of volatiles, a gummy product was obtained which was taken into methylene chloride and potassium carbonate solution. Solids were collected by a filtration, washed with methylene chloride and air dried. The solids (5.3 g) were found to be the potassium salt of the title compound. The basic aqueous filtrate was acidified with concentrated HCl and extracted with methylene chloride to afford 4 g of the title compound, an intermediate useful for the preparation of the compounds of the present invention, melting at 116-7° C. From the methylene chloride used to wash the solids, 2.6 g of the title compound of Step A was recovered. This represented a 71.7% conversion. The combined yield was therefore 96% based on the 71.7% conversion.
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