“…Moreover, this structural moiety has also been explored as a useful synthon for the syntheses of structurally diverse complex heterocycles such as benzo[a]quinazolidine-2-ones, 8 hexahydropyrido[3,4-c][1,5]benzothiazepines, 9 5-(diethoxyphosphoryl)-1-aryl-2-alkyl/aryl-2,3-dihydro-4-pyridones, 10 3-aminopiperidines, 11 methyl indolo[2,3-a]quinazolidin-2-acetate, 12 and synthesis of various alkaloids such as guettardine, 15-epiguettardine, 13 (E)-azaburnamine, 14 makaluvamine A and C, 15 veiutamine, 16 and synthesis of the fundamental tetracyclic skeleton of ervitsine and 20-de-ethylidine-6,16-dihydro analogues. 17 In view of their importance and wide applications, their synthesis has gained considerable attention, and therefore, become a focus of synthetic organic chemistry.…”