5-Substituted 2-amino-4, 6-dihydroxypyrimidines and 2-amino-4, 6-dichloropyrimidines: Synthesis and inhibitory effects on immune-activated nitric oxide production

Abstract

A series of 5-substituted 2-amino-4, 6-dihydr-oxypyrimidines were prepared by a modified condensation of the corresponding monosubstituted malonic acid diesters with guanidine in an excess of sodium ethoxide. The optimized procedure using Vilsmeier-Haack-Arnold reagent, followed by immediate deprotection of the (dimethylamino)methylene protecting groups, has been developed to convert the 2-amino-4, 6-dihydroxypyrimi-dine analogs to novel 5-substituted 2-amino-4, 6-dichloro-pyrimidines in high yields. Pilot screening for biological properties of the prepared compounds was done in mouse peritoneal cells using the in vitro nitric oxide (NO) assay. Irrespective of the substituent at the 5 position, 2-amino-4, 6-dichloropyrimidines inhibited immune-activated NO production. The most effective was 5-fluoro-2-amino-4, 6-dichloropyrimidine with an IC50 of 2 lM (higher activity than the most potent reference compound) while the IC50s of other derivatives were within the range of 9-36 μM. The 2-amino-4, 6-dihydroxypyrimidine counterparts were devoid of any NO-inhibitory activity. The compounds had no suppressive effects on the viability of cells. The Mechanism of action remains to be elucidated.