For evaluating the effectiveness of organic synthesis, both intellectual property factor (IPF) and application potential factor (APF) are proposed. As a representative example, a highly effective synthetic method with IPF value of 53.8 and APF value of 100 has been established starting from indigo directing toward an antibiotic, 6-cyano-5-methoxy-12-methylindolo[2,3-a]carbazole, using only conventional reagents without using any protecting groups.
Short Step Syntheses of a Natural Product, 6-Cyano-5-methoxy-12-methylindolo[2,3-a]carbazole and Novel 6-Aminoindolo[2,3-a]thiazolo[5,4-c]carbazoles