Patent ID: 7799796

Claim:
A compound of formula (I): or a pharmaceutically acceptable salt thereof, wherein: X is: —O—; R 1 is: isopropyl; R 2 , R 5 and R 6 are hydrogen; R 3 is alkoxy; R 4 is halo or —C═C—R a — wherein R a is hydrogen; one of R 7 and R 8 is hydrogen and the other is R 9 , or both R 7 and R 8 are R 9 : and each R 9 is independently: —(C═O)—R d ; —(O═)P(OR g ) 2 ; —S(═O) 2 OR g ; or a mono-, di- or tri-peptide, wherein R d is alkyl, alkoxy, amino, cycloalkyl, cycloalkylalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, heterocyclyl, cycloalkyloxy, cycloalkylalkyloxy, aryloxy, arylalkyloxy, heteroaryloxy, heteroarylalkyloxy, heterocyclyloxy, —(CH 2 ) p —C(═O)—R e , —(CH═CH)—C(═O)—R e , or —CH(NH 2 )—R f ; wherein R e is hydrogen, hydroxy, alkyl, alkoxy, amino, cycloalkyl, cycloalkylalkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, heterocyclyl, cycloalkyloxy, cycloalkylalkyloxy, aryloxy, arylalkyloxy, heteroaryloxy, heteroarylalkyloxy or heterocyclyloxy; p is 2 or 3; R f is hydrogen, alkyl, hydroxyalkyl, aminoalkyl, optionally substituted phenyl, benzyl, guanidinylalkyl, carboxyalkyl, amidoalkyl, thioalkyl or imidazolalkyl; and R g is hydrogen, alkyl, an alkali metal ion or an alkaline earth metal ion.