Next, we broadened our aminoacyl-mixed anhydride scope in the first step to include leucyl-and prolyl-residues (Leu and Pro respectively). For the second transfer, fAla-or fGly-mixed anhydride pentamer donor strand were used as with previous experiments (Fig. , Table , Fig. ). Transfers of fAla onto Leu-or Pro-acceptors produced four new HPLC peaks with identical kinetics, whilst transfers of fGly onto Leu or Pro produced two new ones. This is consistent with both the racemisation of fAla and a resolution of the mixture of 2'/3'-esters in the products. We did not further differentiate these peaks. HPLC and MALDI analysis confirmed that all four 2'/3'-formyl-dipeptidylesters were correctly synthesized, with distinct yields and synthesis/hydrolysis kinetics.