合成路线1

The synthetic route from 8-aminopenicillanic acid (6-APA) to title compound is depicted in scheme. Diazotization of 6-APA (I) in the presence of Br2, followed by conventional esterification (MeI), gives the dibromopenicillanate (II), whose magnesium enolate (EtMgBr) is condensed with acetaldehyde to stereoselectively afford the bromohydrin (III). Debromination (Zn/MeOH) gives the trans-penicillanate (VI), which, via a two-step demolition of the thiazolidine ring [Hg(OAc)2, then KMnO4], is converted to the key azetidinone intermediate (IX). Acetate displacement with a suitable rhioacid (prepared trom glycolic acid after silylation of the hydroxy group) yields (XI). N-Oxalylation of the latter, followed by an original phosphite-mediated dicarbonyl coupling, gives the penem (XIV). Selective deblocking of the primary hydroxyl (Bu4NF) and exposure to trichloroacetylisocyanate results in the fully protected precursor (XVI), with is first unmasked in positions 2,8 (Bu4NF) and then in position 3 (Pd(0)-catalyzed deallylation in the presence of Na ethylhexanoate) to afford the sodium salt (FCE-22101).