Patent ID: 6995261

Claim:
A compound of the formula (I) or a pharmaceutically acceptable salt thereof: wherein R 1 is halogen, alkyl sulfonate, aryl sulfonate, alkyl phosphonate, aryl phosphonate, alkyl phosphate or aryl phosphate; R 2 is OR 5 , NH(CHR 5 ) m —COOR 5 , N(R 5 )R 6 or NH(CHR 5 ) m OH; R 3 is H or alkyl; R 4 is H, aryl, heteroaryl or alkyl, wherein said R 4 aryl is selected from the group consisting of substituted naphthyl, unsubstituted naphthyl, and substituted phenyl, and wherein the substituents of said R 4 substituted phenyl are selected from the group consisting of halo, lower alkyl, nitro, amino, acylamino, hydroxy, lower alkoxy, alkyl sulfonyl, trifluoromethyl, morpholinoethoxy, morpholinosulfonyl and carbobenzoxy-methyl sulfonyl; R 5 and R 6 are independently H, lower alkyl, aryl, hydroxy alkyl, amino alkyl, heteroaryl, lower alkylene-aryl, lower alkylene-heteroaryl or lower cycloalkyl; m is 0–6; and provided that when R 1 is chloro, R 3 is H and R 2 is NH 2 , R 4 is not 3- or 4-pyridyl.