Prodrugs of paclitaxel derivatives

Claim 1

A compound of formula I, or a pharmaceutically acceptable salt thereof wherein R 1 is hydroxy, -OC(O)R x or -OC(O)OR x ; R 2 is hydroxy, hydroxy, -OC(O)R x or -OC(O)OR x ; R 2' is hydrogen, hydroxy or fluoro; R 6' is hydrogen or hydroxy; R 6 is hydrogen, or R 2 and R 6 together can form oxirane ring or a bond; R 3 is hydrogen, hydroxy, C 1-6 alkyloxy, -OCONR 11 R 12 , -OC(O)R x or -OC(O)OR x ; R 8 is methyl or hydroxymethyl, or R 8 and R 2 together can form cyclopropane ring; R 9 is hydroxy or -OC(O)R x ; with the proviso that when R 8 and R 2 form cyclopropane ring, R 2' is hydrogen; when R 2 and R 6 form oxirane ring or double bond, R 2' and R 6' are hydrogen; when R 2 is hydroxy, -OC(O)R x or -OC(O)OR x , R 2' is hydrogen; when R 2' is fluoro, R 2 is hydrogen; one of R 7 or R 7' is hydrogen and the other is hydroxy, -OC(O)R x or -OC(O)OR x , or R 7 and R 7' together can form an oxo group; R 11 and R 12 are independently C 1-6 alkyl, hydrogen, aryl or substituted aryl; R 4 and R 5 are independently C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, or -Z-R 10 ; Z is a direct bond, C 1-6 alkyl or C 2-6 alkenyl; R 10 is aryl, substituted aryl, C 3-6 cycloalkyl or heteroaryl; p is 0 or 1; R d and R e are independently hydrogen, C 1-6 alkyl, aryl, substituted aryl or phosphono protecting group; R f is hydrogen or hydroxy; R x is C 3-6 cycloalkyl, C 2-6 alkenyl or C 1-6 alkyl, all can be optionally substituted with one to six same or different halogen atoms; or R x is a radical of the formula wherein D is a bond or C 1-6 alkyl; and R a , R b and R c are independently hydrogen, nitro, amino, C 1-6 alkylamino, di-C 1-6 alkylamino, halogen, C 1-6 alkyl, hydroxy or C 1-6 alkoxy.