this invention features pyrimidine compounds of formula : r 1 is each of r 2 and r 4 is h ; r 3 is h , alkyl , aryl , heteroaryl , cyclyl , heterocyclyl , or alkylcarbonyl ; r 5 is h or alkyl ; n is 0 , 1 , 2 , 3 , 4 , 5 , or 6 ; x is nr c ; y is covalent bond , ch 2 , c , c ═ n — r c , c ═ n — or c , c ═ n — sr c , o , s , s , s , or nr c ; z is n or ch ; one of u and v is n , and the other is cr c ; and w is o , s , s , s , nr c , or ncr c ; in which each of r a and r b , independently , is h , alkyl , aryl , heteroaryl ; and r c is h , alkyl , aryl , heteroaryl , cyclyl , heterocyclyl , or alkylcarbonyl .