A convenient synthesis of indole-substituted 2-pyrrolidones and their cyclized derivatives

Condensation between indole, Meldrum's acid, and benzyloxycarbonylacetaldeh yde or aminoacetaldehyde derivatives yielded trimolecular adducts 7a-c. The latter were cyclized to indole-substituted 2-pyrrolidones 15a-b or 3-amino pyrrolid-2-ones 18a-b, depending on the starting material. Derivative 18a w as transformed into pyrrolo[3',4' :5,6]pyrido[3,4-b]indol-3(2H)-ones 19a an d 20a by a Pictet-Spengler condensation with benzaldehyde.