The invention relates to the field of organic chemistry and medicine, and more particularly to synthetic substances of the pyrimidine series, namely 2-chloro-5-phenyl-5 H- pyrimido[5' , 4' : 5, 6]pyrano[2, 3-d]pyrimidine-4-ol derivatives, having antiviral activity. Claimed are a drug with antiviral activity against HIV infection and hepatitis B virus, containing 2-chloro-5-phenyl-5H-pyrimido[5' , 4' : 5, 6]pyrano[2, 3-d]pyrimidine-4-ol derivatives of the general formula shown, where : X is selected from the group : H, NO 2 , Hal, OMe; R1 is selected from the group : Cl, OH; and R2 is selected from the group : Cl, SH, OH; and a drug with antiviral activity against HIV infection, containing a 2-chloro-5-phenyl-5H-pyrimido[5' , 4' : 5, 6]pyrano[2, 3-d]pyrimidine-4-ol derivative of the general formula shown, where : X is selected from the group : H, NO 2 , Hal, OMe; R1 is selected from the group : Cl, OH; and R2 is selected from the group : Cl, SH, OH in combination with a reverse transcriptase inhibitor selected from Retrovir, or in combination with a protease inhibitor selected from Lopinavir, in an effective amount. The result is an effective drug with antiviral activity.