合成路线1

7-Aminocephalosporanic acid (I) was esterified with diphenyldiazomethane to produce the benzhydryl ester (II). Diazotization of (II) with isopropyl nitrite in the presence of trifluoroacetic acid, followed by treatment of the resulting diazo compound with propylene oxide and a catalytic amount of rhodium (II) octanoate, gave the corresponding 7-oxocephalosporanate (III). Wittig reaction of ketone (III) with the ylide resulting from 2-picolyltriphenylphosphonium chloride (IV) and NaNH2 in cold THF yielded olefin (V). Cephem double-bond isomerization upon treatment with triethylamine produced the 2-cephem derivative (VI) as the major compound, which was separated from the unreacted 3-cephem by flash chromatography. Acid hydrolysis of acetate ester (VI) gave rise to the corresponding alcohol (VII), which was further oxidized to aldehyde (VIII) by using pyridinium dichromate. Condensation of aldehyde (VIII) with the Wittig reagent (III) produced adduct (IX).