New scaffolds for peptidomimetics. Synthetic approaches towards 2,4-dioxooctahydropyrimido[1 ',6 ': 1,2]pyrido[3,4-b]-indole-6-carboxylic acid derivatives

The synthesis of 6-substituted 2,4-dioxooctahydropyrimido[1',6':1,2]pyrido[ 2,3-b]indole derivatives from 1-(alkyloxycarbonyl)methyltetrahydro-beta-car boline-3-carboxylic acid derivatives is described. The construction of the pyrimidine ring competes with that of the imidazole, to provide imidazo[1', 5':1,6]pyrido[2,3-b]indole derivatives, when an alkyloxycarbonyl group is p laced in position 3 of the tetrahydro-beta-carboline, but not when there is a carboxamide function in such position.