What's the main difference between vasopressin and desmopressin?

Modified amino acids: Vasopressin is a naturally occuring peptide hormone - a chain of Amino Acids linked together. Desmopressin is a synthetic peptide with substitution of two different Amino Acids (cystine at the 1 position is changed to a deaminated form; and the arginine at the 8 position is the d form instead of the l form used in all naturally occuring peptides and proteins).