Total Synthesis of Coumarinolignans, Propacin and Its Regioisomer

Abstract

Compound 8 was reacted with 7 in the presence of potassium tert-butoxide to give the condensation product (9), which was reduced with lithium borohydride to afford a mixture of alcohols (10a, b). The alcohols underwent cyclization with concentrated hydrochloric acid to furnish propacin (1). Its regioisomer (3) was also synthesized from the condensation product (13) through a similar route.