Azetidinepropanoic acid derivative (I) was converted to the mixed anhydride with isobutyl chloroformate and then coupled with N,O-dimethylhydroxylamine to afford the N-methoxyamide (II). This was treated with 2-thiazolylmagnesium bromide (III) to give thiazolyl ketone (IV). Condensation of (IV) with allyl glyoxylate hydrate (V) produced adduct (VI). Further reaction of (VI) with SOCl2 and then with triphenylphosphine gave the corresponding phosphorane, which cyclized in boiling anisole to generate the carbapenem (VII). After N-methylation at the thiazole ring of (VII) with methyl triflate, the thiazolium salt (VIII) was reduced with NaBH4 and subsequently hydrolyzed to aldehyde (IX) in the presence of HgCl2. Addition of isopropylmagnesium bromide to (IX) at -78 C, followed by desilylation with tetra-butylammonium fluoride yielded diol (X). Then, palladium-catalyzed deprotection of the allyl ester of (X) in the presence of sodium 2-ethylhexanoate provided the sodium carboxylate salt (XI). Finally, reaction of (XI) with 1-iodoethyl isopropyl carbonate (XII) in cold DMF produced the target ester.

Azetidinepropanoic acid derivative (I) was converted to the mixed anhydride with isobutyl chloroformate and then coupled with N,O-dimethylhydroxylamine to afford the N-methoxyamide (II). This was treated with 2-thiazolylmagnesium bromide (III) to give thiazolyl ketone (IV). Condensation of (IV) with allyl glyoxylate hydrate (V) produced adduct (VI). Further reaction of (VI) with SOCl2 and then with triphenylphosphine gave the corresponding phosphorane, which cyclized in boiling anisole to generate the carbapenem (VII). After N-methylation at the thiazole ring of (VII) with methyl triflate, the thiazolium salt (VIII) was reduced with NaBH4 and subsequently hydrolyzed to aldehyde (IX) in the presence of HgCl2. Addition of isopropylmagnesium bromide to (IX) at -78 C, followed by desilylation with tetra-butylammonium fluoride yielded diol (X). Finally, palladium-catalyzed deprotection of the allyl ester of (X) in the presence of sodium 2-ethylhexanoate provided the title sodium carboxylate salt.

The oxidation of the hydroxymethyl carbapenem (I) with MnO2 in refluxing dichloromethane gives the corresponding aldehyde (II), which is treated with isopropylmagnesium chloride in THF yielding, after chromatographic separation, the 1(R)-hydroxy-2-methylpropyl derivative (III). Finally, this compound is deprotected with Pd(PPh3)4 and converted to the sodium salt with sodium 2-ethylhexanoate (SHE).