The silylation of 3'-iodocephalosporin (I) with Tms-Br in dichloromethane gives the trimethylsilyl ester (II), which is oxidized with MCPBA in the same solvent to yield the sulfoxide (III). Finally, this compound is condensed with the sodium salt of all-trans-beta-retinoic acid (IV) in DMF to afford the target conjugate.