Convenient synthesis of (RS)-4-amino-3-hydroxybutyric acid. 
A new three-step synthesis of 4-amino-3-hydroxybutyric acid from an inexpensive starting material and under mild reaction conditions is described.  Crotonic acid was brominated by the Wohl-Ziegler reaction to 4-bromocrotonic acid, which, in turn, was converted with ammonium hydroxide into 4-aminocrotonic acid.  This compound, refluxed in water in the presence of a strong acid resin, afforded 4 amino-3-hydroxybutyric acid in good yields.