A mixture of 2,7-diamino-6-(2,6-dichlorophenyl)-pyrido[2,3-d]pyrimidine (3.0 g) from Example 1, sulfamic acid (1.9 g), and 1-(3-aminopropyl)-4-methylpiperazine (15 mL) was heated to approximately 150° C. for 24 hours. After cooling, the residue was dissolved in water. The aqueous solution was made alkaline with a solution of saturated sodium bicarbonate and extracted with dichloromethane several times. The dichloromethane layers were combined, dried over magnesium sulfate, and concentrated in vacuo. The residue was recrystallized from ethyl acetate to give 2.0 g of 6-(2,6-dichlorophenyl)-N2 -[3-(4-methyl-piperazin-1-yl)-propyl]-pyrido[2,3-d]pyrimidine-2,7-diamine, CIMS (1% NH3 in CH4): 474=M+ +C2H5, 446=M+ +H (Base); mp 208°-211° C.
