Aspoxicillin (CAS NO.: ), with other name of N4-Methyl-D-aspariginylamoxicillin, could be produced through the following synthetic routes.

The reaction routes are as below:

The reaction of 2-amino-3-(N-methylcarbamoyl)propionic acid (I) with 2-nitrophenylsulfonylchloride (II) by means of K₂CO₃ in THF gives 2-(2-nitrophenylsulfonylamino)-3-(N-methylcarbamoyl)propionic acid (III), which is esterified with N-hydroxysuccinimide (IV) by means of dicyclohexylcarbodiimide in THF yielding the corresponding N-succinimido ester (V). The condensation of (V) with amoxicillin [6-[alpha-amino-alpha-(4-hydroxyphenyl)acetylamino]penicillanic acid] (VI) by means of triethylamine in THF-CHCl₃ affords 6-[alpha[2-(2-nitrophenylsulfonylamino)-3-N-methylcarbamoylpropionamido]-alpha-(4-hydroxyphenyl)acetamido]penicillanic acid (VII). Finally, the sulfonic group is eliminated by treatment with thiobenzamide (A) in ethanol-THF.