Figure 3: An iterative procedure for protection, using the excess of the protected amino acid (L-Ornithine) as an amino component (“nucleophile pool”) and free lipase as a catalyst. After completing the synthesis and after acidification of the reaction mixture, filtering and washing of the precipitated product with water, the combined water phases were extracted with CH2Cl2 or EtOAc to increase the yield and avoid the waste and loss of the product.