The novel photoisomerization of 1-acylindoles accompanied by a conversion of indole to indolenine afforded 3-acylindolenines, a so far unknown reactive species, as a major product. This reaction was thorougly investigated and applied with success to the total synthesis of Strychnos, Aspidosperma, Schizozygane and Eburnamine alkaloids through a versatile intermediate 9-membered ring system, synthesized