How is 4-Nitrobenzyl 3-oxobutanoate (CAS: 61312-84-3) typically synthesized?

4-Nitrobenzyl 3-oxobutanoate is typically synthesized via a multi-step process involving the formation of a nitrobenzyl ester followed by the introduction of a 3-oxobutanoate moiety. Common methods include the reaction of 4-nitrobenzyl chloroformate with 3-oxobutanoic acid in the presence of a catalytic amount of a base, such as triethylamine, with yields of up to 90%.