fostedil 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. fostedilclinical dataroutes ofadministrationoralatc codenonelegal statuslegal status in general: uncontrolled identifiers iupac name diethyl phosphonate cas number75889-62-2pubchem cid53421chemspider48253uniid41ws786ulkeggd04260chemblchembl39516comptox dashboard (epa)dtxsid70226811 chemical and physical dataformulac18no3psmolar mass341.24 g·mol−13d model (jsmol)interactive image smiles o=p(occ)(occ)cc3ccc(c1nc2ccccc2s1)cc3 synthesis fostedil synthesis: treatment of benzanilide with phosphorus pentasulfide or lawesson's reagent gives thioamide. oxidative ring formation by reaction with potassium ferricyanide and base (presumably involving a free radical intermediate) constructs the benzothiazole ring. bromination of this compound with n-bromosuccinimide produces bromomethyl intermediate. the synthesis of fostedil concludes with a michaelis-arbuzov reaction with triethyl phosphite.