Facile synthesis of ortho-halo-substituted 4-aryl-2-aminobutyric acids

Herein we describe ail efficient and practical route for the regioselective synthesis of 4-(5-bromo/chloropyrazol-1-yl)-2aminobutyric acids. The compounds have been prepared by regioselective C-5 halogenation of 1-(3,3-dimethoxypropyl)-1H-pyrazole followed by a Strecker synthesis. In addition, Boc-protected 2-amino-4-(2-chlorophenyl)butyric acid and 2-amino-4-(3-chloropyridin-2-yl)butyric acid have been synthesized.