2.2. Synthesis of Anionic DSDAs from Cilastatin

The anionic DSDAs from cilastatin were obtained via amidation between the free α-amino group of cilastatin and decanoyl or oleoyl chloride (C₁₀ or C₁₈, respectively). The reaction was performed as published in our previous publication [38], with minor modifications. Cilastatin (1 g, 2.8 mmol, 1 equiv.) was dissolved in THF (10 mL) and the mixture was stirred at room temperature until the compound was completely dissolved. In another flask, a solution of NaOH (390 mg, 9.76 mmol, 3.5 mmol) in 10 mL of H₂O was prepared. When this solution was cooled down, it was slowly added dropwise to the other mixture containing the cilastatin in THF with moderate stirring in an ice bath. After the addition, the corresponding carbonyl chloride (decanoyl or oleoyl chloride; 2.8 mmol, 1 equiv.) in THF (5 mL) was added dropwise over a period of 10 min. After that, the reaction was stirred overnight and let to reach room temperature. Then, water and hydrochloric acid were added until the mixture was brought to pH 2–3. The aqueous layer was then extracted with EtOAc (3 × 50 mL) and the combined organic layer were washed with H₂O and brine (2 × 50 mL). The solvent was reduced under pressure to yield the corresponding lipidic derivative of cilastatin that was characterized by ¹H and ¹³C NMR.