合成路线1

A short-step synthesis of CS-834 has been described: The condensation of azetidinone (I) with pyrrolidinone (II) by means of CDI gives the thioester (III), which is desilylated with BF3/Et2O to the alcohol (IV). In order to have a more labile protecting group, alcohol (IV) is resilylated with TMS-Cl (or TES-Cl) and triethylamine affording the silyl ether (V), which is protected again at the pyrrolidine nitrogen with TES-Cl, affording the disilylated azetidinone (VI). The condensation of (VI) with the oxalyl chloride (VII) by means of triethylamine in dichloromethane gives the expected oxalylazetidinone (VIII), which is treated with diethyl ethylphosphonite in toluene yielding the ylide (IX). This compound, without isolation, is cyclized in refluxing mesitylene to afford the protected carbapenem intermediate (X), which is finally desilylated with HCl in acetonitrile. The cyclization of azetidinone (VIII) to carbapenem (X) can also be performed with triethyl phosphite instead of diethyl ethylphosphonite. The oxalyl chloride (VII) is obtained by monoesterification of oxalic acid (XI) with pivaloyloxymethyl iodide (XII) by means of triethylamine yielding monoester (XIII), which is finally converted to intermediate (VII) by treatment with oxalyl chloride in dichloromethane.