A second generation polyphosphoric acid-mediated one-pot three-component synthesis of indoloquinoline scaffold is developed. This improved version of the process involves electrophilically activated nitroalkanes for the installation of strategic C–C and C–N bonds and ring C assembly. This modification allows the elimination of unnecessary solvent change operations and all steps are carried out in a true, uninterrupted one-pot manner. A further improvement involves the possibility to install an ortho-amino group in situ. A synthetic application of this method is showcased by the concise synthesis of an isocryptolepine alkaloid and its synthetic analogs with potent anticancer activities.
Aksenov NA, Aksenov AV, Kornienko A, De Carvalho A, Mathieu V, Aksenov DA, Ovcharov SN, Griaznov GD, Rubin M. A nitroalkane-based approach to one-pot three-component synthesis of isocryptolepine and its analogs with potent anti-cancer activities. RSC Adv. 2018 Nov 1;8(64):36980-36986. doi: 10.1039/c8ra08155g. PMID: 35558925; PMCID: PMC9089289.