Dodecapeptide ester Ⅰ has been saponified to give a protected C-terminal dodeca-peptide (Ⅱ) of the A-Chain of insulin^[1]. Further experiments showed that the saponification of ester Ⅰ under various conditions yielded preparations of dodecapeptide Ⅱ varying somewhat in melting points and solubility. These saponification products have been used for the partial synthesis of bovine insulin and all the crude hormone products obtained showed biological activity of 1-4% of natural insulin in mouse convulsion test. In order to avoid the saponification dodecapeptide Ⅱ has been directly synthesized by two alternative routes.