Du Vigneaud, du VEEN yoh, Vincent (1901-1978), was an American biochemist who won the 1955 Nobel Prize for chemistry for his work on biologically important compounds containing sulfur. He was honored especially for his synthesis (laboratory production) of two hormones, vasopressin and oxytocin. The synthesis of any substance is vital to research chemists, because it confirms their ideas of the composition and structure of the molecule.