[CH:1]1([O:7][N:8]=C(C2N=C(N)SC=2)C(O)=O)[CH2:6][CH2:5][CH2:4][CH:3]=[CH:2]1.O.P(Cl)(Cl)([Cl:22])=O.C[Si](CC(N)=O)(C)C>O1CCCC1.CN(C)C=O>[ClH:22].[CH:1]1([O:7][NH2:8])[CH2:6][CH2:5][CH2:4][CH:3]=[CH:2]1A solution of 2-(2-cyclohexen-1-yl)oxyimino-2-(2-aminothiazol-4-yl)acetic acid (syn isomer) (1.91 g: This material contains 8% of water) in tetrahydrofuran (20 ml) was stirred at below 5° C. To the solution was added phosphoryl chloride (1.4 g) and the stirring was continued for 20 minutes at below 5° C. To the solution was added trimethylsilylacetamide (1.11 g: This reagent contains 8% of water) and the stirring was continued for 20 minutes at the same temperature. And to the solution was added phosphoryl chloride (1.4 g) and the stirring was continued for 20 minutes at the same temperature. To the resulting solution was added N,N-dimethylformamide (0.65 g) and the stirring was continued for additional 30 minutes to give the solution A. A solution of 7-aminocephalosporanic acid (1.9 g) and trimethylsilylacetamide (5.6 g) in ethyl acetate (40 ml) was stirred for 15 minutes at 40° C. and then cooled to -25° C. To the resulting solution was added the above obtained solution A and then the mixture was stirred for an hour at -15° C. After the addition of ethyl acetate and water to the reaction mixture, the organic layer was separated, washed with a saturated aqueous solution of sodium chloride, dried over magnesium sulfate and then evaporated. The residue was adjusted to pH 6.5 with a saturated aqueous solution of sodium bicarbonate and subjected to column chromatography on alumina using 5% sodium acetate as an eluent to give 7-[2-(2-cyclohexen-1-yl)oxyimino-2-(2-aminothiazol-4-yl)acetamido]cephalosporanic acid (syn isomer) (0.5 g).
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