Catalytic hydrogenolysis of benzyl ester (VII) affords carboxylic acid (VIII) (1). Then, coupling of acid (VIII) with ampicillin (IX) using isobutyl chloroformate provides the target adduct, which is finally converted to the title sodium salt upon treatment with sodium 2-ethylhexanoate in EtOAc.
Acylation of L-lysine (I) with 2,3-diacetoxybenzoyl chloride (II) provides the dibenzoyl lysine derivative (III). After activation of (III) as the corresponding mixed anhydride with isobutyl chloroformate, condensation with alpha-benzyl L-glutamate (IV) yields the dipeptide compound (V). This is further coupled with N-(benzoyloxy) methylamine (VI), via the mixed anhydride with isobutyl chloroformate, to furnish hydroxamate (VII).