Pyrido [2, 3‐d]pyrimidines and Pyrimido[5′, 4′:5, 6]pyrido[2, 3‐d]pyrimidines as New Antiviral Agents: Synthesis and Biological Activity

A series of 7‐amino‐ and 7‐oxo‐5‐aryl‐6‐cyanopyrido[2, 3‐d]pyrimidines, 4 and 11, respectively, and pyrimido [5′, 4′:5, 6]pyrido[2, 3‐d]pyrimidine derivatives 6 and 7 was synthesized and investigated as antiviral agents. Different synthetic strategies for the preparation of the target compounds were explored. A synthetic procedure for 4 and 11 starting with 6‐amino‐1, 2, 3, 4‐tetrahydro‐2, 4‐dioxopyrimidine, proper aldehyde, and malononitrile or ethyl cyanoacetate, respectively, in a one‐pot reaction proved to be the method of choice for preparation of compounds of such type. Construction of another pyrimidine ring on the pyridine nucleus of compound 4 was achieved either by reaction with phenyl iso(thio)cyanate or with formic acid to yield 6 and 7, respectively. The structure of the prepared compounds was confirmed through elemental analysis and spectral investigation. Most of the newly synthesized compounds were subjected to antiviral activity testing against herpes simplex virus (HSV) where some of them show good activities.