Reaction SMILES: [NH2:1][CH:2]1[C:17](=[O:18])[N:4]2[C:5]([C:14]([OH:16])=[O:15])=[C:6]([CH2:9][O:10][C:11](=[O:13])[CH3:12])[CH2:7][S:8][C@H:3]12.C[Si](C)(C)NC(O[Si](C)(C)C)=C.C(O[CH:34](OCC)[CH2:35][N:36]=[C:37]=[N:38][Si](C)(C)C)C.S(=O)(=O)(O)O>C(#N)C>[C:11]([O:10][CH2:9][C:6]1[CH2:7][S:8][C@@H:3]2[CH:2]([NH:1][C:37]3[NH:36][CH:35]=[CH:34][N:38]=3)[C:17](=[O:18])[N:4]2[C:5]=1[C:14]([OH:16])=[O:15])(=[O:13])[CH3:12]
Reactant: CC(=O)OCC1=C(C(=O)O)N2C(=O)C(N)[C@H]2SC1
Reactant: CCOC(CN=C=N[Si](C)(C)C)OCC
Agent: C=C(N[Si](C)(C)C)O[Si](C)(C)C
Agent: O=S(=O)(O)O
Solvent: CC#N
Product: CC(=O)OCC1=C(C(=O)O)N2C(=O)C(Nc3ncc[nH]3)[C@H]2SC1
Temperature: 0 °C
Reaction time: 2.5 h
Yield: 58.3 %

Procedure:
To a stirred mixture of 7-amino-3-acetoxymethylceph-3-em-4-carboxylic acid (5.44 g.) and acetonitrile (25 ml.) under argon at ambient temperature (22°-24°) was added N-trimethylsilyl-1-trimethylsilyloxyvinylamine (4.93 ml.) over 2 minutes and the mixture stirred at ambient temperatures for 2.5 hours to give a clear orange solution. To this solution, cooled in ice, was added 1-(2,2-diethoxyethyl)-3-trimethylsilylcarbodiimide (4.6 g.) over 2 minutes, followed by conc. sulphuric acid (1.06 ml.) over 13 minutes, the temperature of the reaction mixture being maintained below 7°. The solution temperature was maintained at 0° for 30 minutes, then more 1-(2,2-diethoxyethyl)-3-trimethylsilylcarbodiimide (0.46 g.) and more conc. sulphuric acid (95 1.) were added, the temperature of the reaction mixture being maintained below 3°. After another 30 minutes at 0° further additions of the same amount of these reagents were made. The golden yellow solution was maintained at 0° for 1 hour and then (for convenience) stored at -20° under argon for 2 days. To this solution of trimethylsilyl 3-acetoxymethyl-7-[2-(2,2-diethoxyethyl)-3-trimethylsilyl]guanidinoceph-3-em-4-carboxylate stirred in an ice bath was added boron trifluoride acetic acid complex (40% w/w; 7.3 ml.) over 6 minutes, the temperature of the reaction mixture being maintained below 5°. The temperature of the solution was maintained at 0°-1° for 7.5 hours and then (for convenience) stored at -20° under argon for 18 hours. The solution was diluted with ice-cold water (100 ml.), the temperature of the mixture being maintained below 5° and then extracted with cold dichloromethane (60 ml.; 2×40 ml.). The aqueous layer was diluted with more ice-cold water (100 ml.) and the pH adjusted to 4 with 9N aqueous sodium hydroxide solution (10 ml.). The solution was applied to a column of Diaion HP-20 resin (160 ml. bed volume) made up in deionised water. The resin was washed with water (160 ml.) and then the product was eluted with acetonitrile/water 20:80 v/v. The fraction (ca. 110 ml.) rich in product was allowed to stand for 1 hour at room temperature whereupon the product cyrstallised out as finse colourless needles. The mixture was stored at 0° for 2 days and the solid was filtered off, washed with cold acetonitrile (2×5 ml.) and dried in vacuo to give 3-acetoxymethyl-7-(imidazol-2-yl)aminoceph-3-em-4-carboxylic acid (3.94 g.) having the following analysis: strength (HPLC comparison with an authentic sample of known strength) 88.5%, water content 9.7%.