| abstract |
Compounds are provided having formulae (I) and (II) wherein n is 0 or 1 and when n=1, R is a 5 or 6 membered heterocyclic ring, hydroxy, halogen, oxo, carbamoyl, alkoxy, or disubstituted amino, when n=0, R is an ester, cyano or amide group; X is CH or NH; R3 is cyano, methoxy, or acetamido; R1 is hydrogen, alkyl, a negative charge, a cation selected from the group consisting of sodium, potassium and tetraalkylammonium and acyloxyalkyl, or alkoxycarbonyloxyalkyl; and R2 is hydrogen, acyl, trisubstituted silyl carbamoyl or an amino acid residue; or pharmaceutically acceptable salts thereof. |