The synthesis of MD-39-AM (V) was carried out as follows: From 2-chloronicotinic acid (as its acyl chloride) (I) and thiourea in triethylamine (1:1:2), compound (II) was obtained. However, in order to avoid the substitution of 2-Cl by sulfur, 2-methylisothiourea was used. By boiling a solution of (II) in dimethylformamide (DMF) for 15 min, (III) (87%) was obtained. Reaction of (III) with phosphorous oxychloride gave 4-chloro-2-(methylthio)pyrido[2,3-d]pyrimidine (IV) (90%). By reacting (IV) with aniline in ethanol, MD-39-AM was obtained.