Fostedil

Fostedil (A-53,986, KB-944) is a vasodilator acting as a calcium channel blocker which was under development for the treatment of heart conditions such as angina pectoris but was never marketed. It has antihypertensive and antiarrhythmic effects.

Synthesis

 * 1) Treatment of benzanilide with phosphorus pentasulfide or Lawesson's reagent gives thioamide.
 * 2) Oxidative ring formation by reaction with potassium ferricyanide and base (presumably involving a free radical intermediate) constructs the benzothiazole ring.
 * 3) Bromination of this compound with N-bromosuccinimide produces bromomethyl intermediate.
 * 4) The synthesis of fostedil concludes with a Michaelis-Arbuzov reaction with triethyl phosphite.