Pyrimido[5,4-b]quinolines. III. Synthesis of 10-alkyl-substituted 10-deazaalloxazines

A general method for the synthesis of 10-alkyl-substituted 10-deazaalloxazines (VIII) and the related chemistry are described. 4-Alkyl-substituted 3-aminoquinolines (IV) were reacted with benzoyl chloride and potassium cyanide in methylene chloride-water mixture to obtain Reissert compounds (V) which were hydrolyzed with a mixture of hydrobromic acid and acetic acid, and subsequently with 20% potassium hydroxide to give the corresponding 3-aminoquinaldic acids (VII). Cyclization with urea gave the 10-deazaalloxazines (VIII). Oxidation, hydroxylation and alkylation reactions of the 10-methyl derivatives (VIIIa,b) and of their quinaldic acid precursors are also reported.