Abstract:
Synthesis of pyrimidine annulated quinolines, structurally analogous to biologically active benzonaphthyridines present in alkaloids, has been described. Our synthetic strategy is based on the modified Pictet-Spengler reaction involving substrates comprising deactivated pyrimidine ring as the nucleophilic partner whereas aryl amine originating from the C-4 of the pyrimidine ring served as the source for electrophilic partner. The resulting substrates 5-7 with diversity at 2 and 6-positions after condensation with a variety of aldehydes underwent 6-endo cyclization to furnish pyrimido[5,4-c]quinolines 14 in good yields. However, attempts to further extend this strategy on new structurally analogous substrate, involving the pyridine ring as nucleophilic partner failed; thus limiting the scope of the reaction.
