Total and Diverted Total Synthesis of Pyrrolo-Quinazolinone Alkaloids and Their Analogues

A short and expeditious total and diverted total synthesis of luotonin, vasicinone, and their analogues has been achieved from the key tricyclic quinazolinone intermediate which was accessed from simple substituted anthranilamide obtained from the coupling of & beta;-alanate with isatoic anhydride followed by Dieckmann condensation chemistry of the resulting diester. The tricyclic ketone exhibited interesting chemical properties, e. g. keto-enol tautomerism. Friedlander condensation and Fischer-Indolization were employed for further annulations to access polycyclic alkaloids and their analogues. A short and expeditious total and diverted total synthesis of Luotonin, Vasicinone, and their analogues has been achieved from the key tricyclic quinazolinone ketone that was accessed via Dieckmann condensation chemistry of the diester which was in turn obtained from the isatoic anhydride followed by cyclodehydration. The keto-enol tautomerism of the tricyclic ketone has been studied through 1H NMR. Friedlander condensation and Fischer-Indolization were employed for further annulations on to the tricyclic ketone to yield luotonins and nor-rutaecarpines in good yields.image